Showing papers in "Journal of Pharmacology and Experimental Therapeutics in 1975"

The neurochemistry of Parkinson's disease: effect of L-dopa therapy.

Abstract: Post-mortem brain material from control and Parkinson's disease patients was examined to elucidate further the neurochemistry of this disease and to determine the mechanism of action of L-dopa as a therapeutic agent. The activities of L-aromatic amino acid decarboxylase (dopa D), tyrosine hydroxylase, monoamine oxidase and catechol-O-methyl transferase were examined; in addition the tissue levels of dopa, 3-O-methyldopa, dopamine (DA) and homovanillic acid (HVA) were determined. In the non-dopa-treated Parkinsonian patients, the greatest decreases were detected for striatal DA and dopa D, with homovanillic acid and tyrosine hydroxylase levels showing a lesser change. The activities of monoamine oxidase and catechol-O-methyl transferase in the striatal nuclei were not different from the controls. The putamen was consistently the most severely affected region. Dopa and 3-O-methyldopa were detectable in all brain areas only in those patients treated with L-dopa shortly before death. The mean concentrations of DA in the striatum of these patients were 1) 9 to 15 times higher than those in non-dopa-treated patients, 2) related to the time before death of the last dose of L-dopa and 3) greater in the striatum of patients clinically classified as "good responders" as compared to "poor responders." Although L-dopa therapy increased homovanillic acid levels in all brain areas, a preferential increase was observed in the striatum. It was concluded that L-dopa's principal therapeutic effects in Parkinson's disease are consistent with its transformation to DA in the striatum.

Mechanism of frequency-dependent inhibition of sodium currents in frog myelinated nerve by the lidocaine derivative GEA.

Abstract: A new lidocaine derivative (Astra, GEA 968) depresses excitability of myelinated frog nerve in a manner which depends upon the rate of use of the nerve. This phenomenon has been shown, under voltage clamp conditions, to involve "frequency-" or "use-dependent" inhibition of the transient inward sodium currents at the node of Ranvier. With 0.6 mM GEA 968 in the solution bathing the node, the inward sodium currents produced by 5-msec depolarizing pulses to -20 mV are reduced to 40% of control values if the node is rested for a few hundred seconds prior to the test pulse. Repetitive opening of the sodium channels by depolarizing pulses enhances this inhibition, for example, currents are eventually reduced to 10 to 20% of control with repetitive depolarization at 2 sec-1. If the preparation is then allowed to rest, this use-dependent increment in inhibition gradually declines with a time constant of about 10 seconds. Repetitive opening of the sodium channels by depolarizing pulses preceded by large hyperpolarizing prepulses reverses the inhibition caused by application of depolarizing pulses alone. It is hypothesized that the GEA 968 molecule binds to open sodium channels and, in doing so, simultaneously blocks the channel and shifts the curve relating sodium inactivation to membrane potential by 20 to 40 mV in the hyperpolarizing direction. Several kinds of evidence supporting this molecular hypothesis are presented. Lidocaine, procaine, procaine amide and a quaternary lidocaine derivative QX-314 also cause use-dependent depression of sodium currents in this preparation. This common mode of action of tertiary and quaternary anesthetics implies that the cationic form of tertiary anesthetics is active.

A new selective inhibitor for uptake of serotonin into synaptosomes of rat brain: 3-(p-trifluoromethylphenoxy). N-methyl-3-phenylpropylamine.

Abstract: 3-(p-Trifluoromethylphenoxy)-N-methyl-3-phenylpropylamine (Lilly 110140) competitively inhibited the uptake of serotonin (5-HT), norepinephrine (NE) and dopamine into synaptosomes of rat brain with Ki values of 5.5 x 10-minus8, 9.5 x 10-minus6 and 1.3 x 10-minus5 M, respectively. Aiming for a more effective inhibitor of 5-HT uptake, we found the trifluoromethyl group in the phenoxy ring was most favorable at the para-position and was better than other substituting groups including fluoro, chloro, methyl and methoxy groups. The N-demethylated (primary amine) and the N.N-diemthylated (tertiary amine) derivatives inhibited the uptake of monoamines with the same effectiveness as Lilly 110140 (a secondary amine). The uptake of 5-HT into synaptosomes was significantly inhibited 15 minutes after an intraperitoneal administration of Lilly 110140. The inhibition persisted for a 24-hour period. NE uptake in vitro maintained a normal rate during the entire time course. Lilly 110140 likewise had no effect on the in vitro and in vivo accumulation of 3-H-tryptophan in the brain. The effect of Lilly 110140 and the tricyclic drug, chlorimipramine, was compared. Although chlorimipramine inhibited the uptake of 5-HT into synaptosomes with same effectiveness as Lilly 110140 in vitro, it reduced the uptake of both 5-HT and NE in vivo. Chlorimipramine exerted its greatest inhibition on the two uptake processes in the 1st hour and none by the 4th hour. Unlike the tricyclic drugs, imipramine, chlorimipramine, desipramine and chlordesipramine, Lilly 110140 and its primary amine derivative did not block the in vivo uptake of NE into rat heart. The present study suggests that Lilly 110140 is a potent and selective inhibitor for uptake of 5-HT into synaptosomes of rat brain.

Intrathecal chemotherapy: brain tissue profiles after ventriculocisternal perfusion.

Abstract: Ventriculocisternal perfusions with five isotopically labeled drugs were performed in the rhesus monkey and the resultant tissue diffusion concentration profiles in caudate nucleus were analyzed. The periventricular distribution space with respect to perfusate concentration was measured and expressed as microliters per 100 mg wet weight: hydroxyurea = 56; methotrexate = 27; thiotepa = 28; 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) = 64 and cytosine arabinoside greater than 170. The apparent diffusion constants in caudate nucleus were determined for hydroxyurea and methotrexate (2.0 and 1.2 X 10(-6) cm2/sec, respectively); capillary permeability expressed as an extracellular space-transcapillary exchange half-time was estimated to be greater than 2 hours for both compounds. The extracellular fluid-transcapillary half-time was measured for thiotepa and BCNU (1.0 and 0.8 minute, respectively). Cytosine arabinoside continued to be concentrated by periventricular caudate nucleus during the course of perfusion; perfusate clearance measurements suggest a low capillary permeability. The apparent parenchymal diffusion constant and the capillary permeability of a drug in brain are discussed and are considered useful parameters for predicting drug levels after intrathecal administration.

Effects of thyrotropin-releasing hormone (TRH) on the actions of pentobarbital and other centrally acting drugs.

Abstract: Thyrotropin-releasing hormone (TRH) was found to antagonize pentobarbital-induced sleeping time and hypothermia. While 3 to 100 mg/kg of TRH reduced pentobarbital sleeping time when administered prior to the barbiturate, a dose-response relationship to TRH could not be established. However, doses of 10 to 100 mg/kg of TRH enhanced the lethality of pentobarbital when these compounds were administered simultaneously. Thyrotropin or L-triiodothyronine did not imitate and hypophysectomy did not reduce the effects of TRH, indicating that the pituitary is not essential for its antagonism of pentobarbital. Studies of TRH analogs provided further support of this view. In addition, TRH reduced the sleep and hypothermia produced by thiopental, amobarbital, secobarbital and phenobarbital, and it antagonized the hypothermia and reduced motor activity produced by chloral hydrate, reserpine, chlorpromazine and diazepam. Intracisternally administered TRH also reduced pentobarbital sleeping time and hypothermia, but melanocyte-stimulating hormone release-inhibiting factor and somatostatin administered by this route did not. While reduction of pentobarbital sleeping time by TRH could not be attributed to an affect on monoamine systems or to deamidated TRH, this action was reduced by intracisternally administered atropine, suggesting that cholinergic mechanisms may contribute to the effects of TRH. Thus, the results provide evidence that TRH acts on brain independent of an effect on the pituitary.

Quantification of the analgesic activity of narcotic antagonists by a modified hot-plate procedure.

Abstract: The analgesic activity of morphine and the narcotic antagonists, pentazocine, cyclazocine, levallorphan and nalorphine, was assessed in the rat using two hot plates: one maintained at 49.5 degrees C and the other at the "standard" 54.5 degrees C. The analgesic effects of morphine using the 49.5 degrees C hot plate were of a significantly greater magnitude than its effects using the 54.5 degrees C hot plate for both nontolerant and morphine-tolerant subjects. Dose-related effects were observed with all of the narcotic antagonists tested using the 49.5 degrees C hot plate; only the highest dose of pentazocine exhibited activity using the 54.5 degrees C hot plate. Naloxone (3.0 mg/kg) antagonized the analgesic effects of morphine and all of the narcotic antagonists, but was without activity itself when tested using the 49.5 degrees C hot plate at doses as high as 30 mg/kg. Aspirin was also inactive using the 49.5 degrees C plate, whereas physostigmine increased latencies only at a dose that produced severe motor deficit. A low temperature hot plate is recommended for evaluating the analgesic activity of narcotic antagonists in the rat. This simple procedure provides results which are dose-related, quantifiable, reproducible, of a large magnitude and specific.

Comparative studies of substrates and inhibitors of choline transport and choline acetyltransferase.

Abstract: Analogs of choline and three hemicholinium derivatives were studied as substrates for choline acetyltransferase (ChAc) and as substrates or inhibitors of the high-affinity choline transport system in rat brain synaptosomes. Hemicholiniums-3 and -15, but not terphenylhemicholinium-3, were substrates of ChAc. All three inhibit the high-affinity choline transport system, with I50 values of 0.08, 8.0 and 0.08 muM, respectively. Simple choline analogs with substituents on the beta-carbon atom were found to be very poor substrates for ChAc. N-alkyl analogs, mono-, di- and triethyl choline and N-hydroxyethyl pyrrolidinium methiodide (pyrrolcholine), and DL-alpha-methyl choline are substrates for ChAc and also inhibit choline transport, with I50 values between 2 to 6 muM.[3-H] choline, [3-H] monoethycholine and [3-H] pyrrolcholine were transported into synaptosomes by the choline high affinity system and metabolized to acetyl derivatives. The results indicated that choline transport is the rate-limiting step in the biosynthesis of acetylcholine and provide the basis for the development of a group of cholinergic false transmitters.

A choice procedure for drug reinforcers: cocaine and methylphenidate in the rhesus monkey.

Abstract: A choice procedure was developed to compare the reinforcing efficacy of drug solutions delivered via intravenous catheters to rhesus monkeys. Choices were arranged between doses of cocaine or methylphenidate and saline, different doses of the same drug and doses of both drugs. In each session, monkeys were allowed to self-inject one solution five times in the presence of a stimulus. Thirty minutes after the fifth injection, a second solution could be self-injected five times in the presence of a different stimulus. Thirty minutes later, choice trials began in which both stimuli were present and monkeys could choose one of the two solutions. Rate of responding decreased with increases in dose for both cocaine (0.05-1.5 mg/kg) and methylphenidate (0.075-0.7 mg/kg). Response rates maintained by cocaine were 2 to 3 times higher than those maintained by methylphenidate. Drug was always chosen over saline. Higher doses of cocaine were preferred to lower doses except when both were above 0.5 mg/kg, when no preference was shown. Higher doses of methylphenidate were preferred over low doses, but compared to cocaine, a greater absolute difference between dose magnitude was required to demonstrate preference. When equal doses of cocaine and methylphenidate were compared, no preference was shown. On other comparisons between the drugs, the higher dose was generally preferred regardless of the drug. The reinforcing efficacy of drugs must be considered not only in terms of response rate maintained or reinforcement schedule but also with reference to concurrently available drugs.

Amphetamine: evaluation of d- and l-isomers as releasing agents and uptake inhibitors for 3H-dopamine and 3H-norepinephrine in slices of rat neostriatum and cerebral cortex.

Abstract: Release of 3H-doapamine or of 3H-norepinephrine and inhibition of accumulation of 3H-dopamine or 3H-norepinephrine by d- and l-amphetamine were studied in slices of rat neostriatum and in slices of rat cerebral cortex. The two stereoisomers of amphetamine were equally potent as inhibitors of accumulation in the cortex, whereas d-amphetamine was approximately 3-fold more potent than l-amphetamine in the neostriatum. A similar relationship was observed between the two stereoisomers in release experiments. Some spontaneous efflux of 3H-dopamine from tissue slices was evident in absence of added drug in release experiments. When cocaine (2 X 10(-5) M), a known inhibitor of biogenic amine uptake, was added to the medium, there was very little increment in spontaneous efflux of 3H-dopamine in neostriatal slices, but cocaine blocked the release caused by d-amphetamine. This showed that the apparent releasing action of d-amphetamine in the neostriatum was not due to blockade of reuptake of spontaneously released material and that d-amphetamine itself must be taken up to evoke a releasing action. Experiments were designed to compare directly the releasing and uptake inhibiting actions of d-amphetamine. In the cortex, uptake inhibition of 3H-norepinephrine was greater than release over a wide concentration range, while in the neostriatum the two actions were essentially identical in magnitude for 3H-dopamine. We conclude that in the cortex, d-amphetamine can act both to release and to block uptake of 3H-norepinephrine. In the neostriatum, on the other hand, there is releasing action of 3H-dopamine by d-amphetamine (which is stronger than that in the cortex), but the apparent blockade of "uptake" is of questionable significance and appears to result from the release of previously accumulated 3H-dopamine

The effects of the H1 and H2 antihistamines on "allergic" histamine release and its inhibition by histamine.

Abstract: Antigen-induced, IgE-mediated release of histamine from human basophiles is an in vitro model of allergic reacttions; it is blocked by extracellular histamine, presumably as a result of its ability to increase adenosine 3',5'-monophosphate (cyclic AMP) levels. The H1 antihistamines do not antagonize these effects of histamine but at approximately equal to 1 mM cause histamine release and at approximately equal to 0.1mM inhibit antigen-induced histamine release. The phenothiazine antihistamines are 10-30 fold more potent inhibitors than the rest; other tricyclic antidepressant drugs share this activity. The mechanism of this inhibition, which occurs in both the 1 degree and 2 degree stages of histamine release, is not known but it is not due to partial agonist activity since the anti-H1 drugs cause a significant fall in cyclic AMP levels. The anti-anaphylactic effects of the H1 antagonists probably play no therapeutic role but we suggest that drugs structurally similar to the phenothiazine antihistamines should be developed for clinical testing. The H2 antihistamines block histamine-induced inhibition of histamine release and the increase in cyclic AMP levels, but neither cause nor inhibit histamine release. The K-B values for the anti-H2 drugs (burimamide approximately equal to 5 muM); metiamide approximately equal to 0.5muM); are similar to those described for other H2 receptors.

Contractile responses of the guinea-pig trachea in vitro: modification by prostaglandin synthesis-inhibiting drugs.

Abstract: Prostaglandins (PG) E2 and F2alpha, characterized by thin-layer chromatography and bioassay, were released from guinea-pig trachea contracted with acetylcholine or histamine. Inhibition of contraction with atropine or mepyramine, or by the removal of calcium, abolished the prostaglandin release. PGE2 and PGF2alpha were also released after gentle mechanical irritation of the mucosal surface, but not the adventitial surface, of the trachea. This release of prostaglandins occurred in the absence of calcium and was prevented by treatment of the trachea with indomethacin. Incubation (20 minutes) of tracheal spirals with indomethacin (0.6 mug/ml) 1) reduced the basal tension of the spiral; 2) reduced responses to low doses of histamine, serotonin, acetylcholine, barium or potassium; and 3) increased responses to high doses of these agonists. These effects lasted despite washout but were reversed by the addition of arachidonic acid. Subthresholdquantities of PGF2alpha after indomethacin treatment restored responses to minimally effective doses of the agonists. Aspirin (50 mug/ml), 5,8,11,14-eicosatetrayonic acid (2 mug/ml) and sodium salicylate (100 mug/ml) had effects similar to indomethacin (0.6 mug/ml). Alterations produced with 5,8,11,14-eicosatetrayonic acid and sodium salicylate were reversed with washing. Restoration of resting tension after indomethacin did not qualitatively change the results. Indomethacin at higher doses (greater than 30 mug/ml) inhibited responses to all histamine doses but this effect was reversible with washing. The results suggest that basal tension of the guinea-pig trachea may be due to an intramural production of PGF2alpha and that during the development of active tension, prostaglandins E2 and F2alpha are released which modulate the intensity of the contraction.

Effects of ethanol on neurotransmitter release by rat brain cortical.

Abstract: Using a double label technique to preload rat brain cortex slices with different radioactive neurotransmitters (or precursor choline), we have studied the effects of ethanol on the electrically stimulated release of these transmitters. Ethanol inhibited the release of these transmitters, acetylcholine being the most sensitive and occurring at concentrations compatible with moderate to severe intoxication in the rat (IC50 equals 0.17 M). The order of sensitivity to ethanol was acetylcholine greater than serotonin greater than dopamine greater than norepinephrine greater than glutamate greater gamma-aminobutyric acid. Two higher alcohols and two barbiturates were also shown to have a greater inhibitory effect on the stimulated release of acetylcholine than of norepinephrine. The concentrations of all the drugs tested required for 50% inhibition of release of acetylcholine and norepinephrine correlated well with their lipid solubility when corrected for their molecular volumes. The effect of tetrodotoxin and of ouabain on neurotransmitter release was also studied. A comparison of the effects of these two drugs with those of ethanol suggests that the effect of ethanol is consistent with an inhibition of the action potential by this drug, although a specific effect of ethanol on the excitation-coupling process at the synapse cannot by discarded.

Determination and characterization of the antinociceptive activity of intraventricularly administered acetylcholine in mice.

Abstract: Antinociceptive activity of intraventricularly administered acetylcholine was quantitated in mice by the tail-flick and phenylquinone tests. Acetylcholine was administered intraventricularly under light ether anesthesia in a 5 mul volume of sterile saline and mice were retested 10 minutes after the operation. A dose-response curve was established for acetylcholine (ED50 equals 7.3 mug) which was potentiated by intraventricular neostigimine and blocked by intraperitoneal atropine, but not by atropine methyl nitrate or mecamylamine. The antinociceptive effect of morphine was potentiated by intraventricularly administered acetylcholine. The acetylcholine-induced antinocieption was blocked by five narcotic antagonists in the same rank order of potency in which they antagonized the effects of morphine. However, the stereo-specificity of two narcotic antagonists, pentazocine and cylcazocine, was reversed in blocking acetylcholine and morphine-induced antinociception. The results of this study have established a phenomenon of acetylcholine-induced antinociception and identified the central, muscarinic nature of this response. In addition, several experiments have demonstrated similarities between this phenomenon and morphine-induced antinociception. These data implicate the possible involvement of central cholinergic mechanisms in the antinociceptive action of morphine.

Long-term effects of p-chloroamphetamine and related drugs on central serotonergic mechanisms.

Abstract: Earlier studies from our laboratory have demonstrated a marked reduction in the brain level of 5-hydroxytryptamine (5-HT) and in the activity of tryptophan hydroxylase which persists for several weeks after a single dose of 10 mg/kg of p-chloroamphetamine (PCA). In the present study, equally long-lasting decreases were found after the administration of 5 mg/kg of PCA. p-Chloromethamphetamine also caused long-lasting reductions in the level of 5-HT and the activity of tryptophan hydroxylase in brain, whereas the effects of fenfluramine had disappeared 2 weeks after injection. The ability of brain synaptosomes to take up 5-HT was markedly reduced following doses of 2, 5 and 10 mg/kg of PCA. The in vitro addition of PCA to synaptosomal fractions markedly reduced the uptake of dopamine and norepinephrine; however, only a 30% reduction in the uptake of these amines was found in synaptosomes prepared from brains of rats treated with PCA. The effects on catecholamine uptake disappeared within 1 day after injection. In contrast, the time course of recovery of the synaptosomal uptake capacity for 5-HT followed a pattern similar to that found for the recovery of the level of 5-HT and the activity of tryptophan hydroxylase, with a 50% reduction still present 3 months after the injection of 10 mg/kg of PCA. The greatest reductions of 5-HT, tryptophan hydroxylase activity and synaptosomal uptake were found in the midbrain, hippocampus and striatum with less pronounced effects in the hypothalamus, medulla-pons and spinal cord. At both 1 and 14 days after injection of 5 and 7.5 mg/kg of PCA, tryptophan hydroxylase activity in whole brain was reduced by 50% or more; however, 4 days after treatment the activity of the enzyme was reduced only slightly or not at all. The results indicate that different independent mechanisms are responsible for the initial, reversible and the prolonged, irreversible effects of PCA on serotonergic neurons.

Effects of divalent cations, cation chelators and an ionophore on morphine analgesia and tolerance.

Abstract: The analgesic effect of morphine was antagonized in mice by intracerebroventricular injection of Ca++, Mg++ and Mn++ and was potentiated by ethylene glycol tetraacetic acid but was not altered by Sr++, Ba++, Ni++, Hg++, Cd++ or ethylenediamine tetraacetic acid. The antagonistic effect of Ca++ was not altered by pretreatment with pargyline or 6-hydroxydopamine indicating that altered release of catecholamines or serotonin was not involved in this action of Ca++. Induction of morphine tolerance by pellet implantation also did not alter the antagonistic effect of Ca++. The antagonistic effects of Ca++ and naloxone were additive in both nontolerant and tolerant animals and the apparent affinity of naloxone for its receptors, as estimated by in vivo pA2 determinations, was not altered by Ca++. However, the ionophore X537A was found to increase greatly the narcotic antagonist effect of a low dose of Ca++ although the ionophore alone did not alter the effects of morphine. This indicates that Ca"++ must penetrate cell membranes in order to reduce the analgesic effects of morphine. These findings indicate the importance of Ca++ localization in the actions of narcotic agonists and antagonists.

Receptor binding and pharmacological activity of opiates in the guinea-pig intestine.

Abstract: A comparison was made between the affinities of a wide range of opiate agonists, mixed agonist-antagonists and antagonists for opiate receptor binding sites in the guniea-pig intestine longitudinal muscle and myenteric plexus preparation, and their pharmacological potency in influencing the electrically induced contraction of this in vitro functional system. The relative affinities of drugs and the degree of stereospecificity for intestinal binding sites are closely similar to these properties in the brain. Receptor binding correlates extremely well with pharmacological potency, both for agonists and antagonists, indicating that binding involves pharmacologically relevant opiate receptors. Pharmacological activity correlates best with receptor binding assayed in the presence of sodium.

Further properties of stereospecific opiate binding sites in rat brain: on the nature of the sodium effect.

Abstract: Addition of sodium salts has been reported to enhance stereospecific binding of opiate antagonists while reducing binding of agonists to rat brain homogenate. We have tested, in addition to sodium and potassium, a number of organic cations. Our results support the suggestion that the ability to enhace antagonist binding is not a general characteristic of cations or high ionic strength, but a property of sodium ions. We have shown that the increase in antagonist binding results from an enhancement of binding affinity and not from unmasking of new binding sites. The reduction in etorphine binding in the presence of sodium is due to a decrease in binding affinity. This decrease is largely accounted for by an acceleration in the dissociation rate, while the greater affinity of naltrexone binding appears to be due to an increase in rate of association. Our results are consistent with the hypothesis of a conformational change in opiate binding sites in the presence of sodium, transformed sites exhibiting greater affinity for antagonists and reduced affinity for agonists. Preheating of rat brain P2 fraction at 50 degrees C results in gradual inactivation of stereospecific binding, but an increase in naltrexone binding is consistently observed after heating at 50 degrees C for 2 to 3 minutes, even at optimal concentrations of sodium.

D-amphetamine-induced release of "newly synthesized" and "stored" dopamine from the caudate nucleus in vivo.

Abstract: The lateral and third ventricles of anesthetized cats were perfused continuously with artificial cerebrospinal fluid (CSF) containing 3H-tyrosine and the perfusate was analyzed for 3H-catecholamines. The addition of d-amphetamine sulfate to the perfusing CSF for 2 hours, beginning 2 hours after the start of the 3H-tyrosine perfusion, caused an immediate increase in the efflux of 3H-dopamine. The efflux of this amine declined subsequently despite the continued presence of amphetamine in the CSF. The addition of alpha-methyltyrosine to the CSF concurrently with the d-amphetamine did not markedly alter the immediate increase but accelerated the subsequent decline in the efflux of 3H-dopamine. This suggests that ampetamine initially releases dopamine from a "strong pool," but continuous release is dependent upon ongoing amine synthesis. The addition of d-amphetamine to the 3H-tyrosine containing CSF at the start of perfusion immediately increased the efflux of 3H-dopamine. This response was completely blocked by the presence of alpha-methyltyrosine in the CSF. Pretreatment of cats with reserpine effectively depleted the caudate nucleus of endogenous and 3H-dopamine, but did not alter the ability of d-amphetamine to increase the efflux of 3H-dopamine. Indeed, the amount of 3H-dopamine released during each collection period by either intraventricular or intravenous administration of d-amphetamine was higher than the content of the labeled amine remaining in the whole caudate nucleus. These results suggest that damphetamine can release both "stored" and "newly synthesized" 3H-dopamine from the caudate nucleus, but that the maintenance of the amphetamine-induced release of dopamine is dependent upon the newly synthetized pool.

Increased sensitivity to dopaminergic agents after chronic neuroleptic treatment.

Abstract: Male CF-1 mice were treated for 14 days with diets containing haloperidol, thioridazine HCl and 4'-fluoro-4[[4-(p-fluorophenyl)-4-methoxycyclohexyl]-amino]-butyrophenone HCl (U35,777A). At various times during and after neuroleptic treatment, spontaneous and d-amphetamine-stimulated motor activity were measured. Two days after cessation of treatment, the mice displayed enhanced spontaneous and d-amphetamine-stimulated motor activity. This effect was no longer apparent 9 days after neuroleptic intake was terminated. With a quantal test based on the climbing activity induced by apomorphine, it was determined that mice were also supersensitive to apomorphine at 2 days but not 9 days after withdrawal from chronic haloperidol. In an attempt to correlate this supersensitivity to a biochemical parameter related to receptor function, dopamine-stimulated adenyl cyclase activity was assayed in striatal homogenates of mice 2 days after haloperidol withdrawal. No alteration in this parameter was observed. Likewise, the ability of apomorphine to elevate striatal cyclic adenosine monophosphate concentrations in vivo was unaltered by withdrawal from chronic haloperidol. Chronic treatment with neuroleptics results in a brief supersensitivity to dopaminergic agents. This effect does not appear to be accompanied by increases in dopamine-stimulated adenyl cyclase activity in the corpus striatum.

Plasma testosterone levels in heroin addiction and during methadone maintenance.

Abstract: Heroin use was consistently associated with low plasma testosterone levels in narcotic addicts. Heroin addicts maintained on high dosage methadone (80-150 mg/day) also had depressed testosterone levels. Patients on low dosage methadone maintenance (10-60 mg/day) had testosterone levels which were not significant;y different from normal adult male controls. An inverse relationship between methadone dosage and plasma testosterone occurred during methadone detoxification. These findings indicate that heroin and methadone alter male androgen levels with possible derivative effects upon sexual and aggressive behaviors.

Effect of thioridazine, clozapine and other antipsychotics on the kinetic state of tyrosine hydroxylase and on the turnover rate of dopamine in striatum and nucleus accumbens.

Abstract: In rats, a single injection of antipsychotic drugs produced a transitory change in the kinetic state of tyrosine hydroxylase (TH) in striatum and nucleus accumbens. The affinity of TH for 2-amino-4-hydoxy-6,7-dimethyl-5,6,7,8-tetrahydropterine (DMPH4) and the Vmax with respect ot tyrosine were increased. The relative potencies of anti-psychotics to change the kinetics of TH in striatum and nucleus accumbens when injected into rats were measured in the presence of 0.4 mM DMPH4. The doses of methiothepin, pimozide and halopridol which increased the affinity for DMPH4 of striatal TH were lower than those required to produce a similar change in nucleus accumbens. In contrast, thioridazine and clozapine were more effective in nucleus accumbens than in striatum. Chlorpromazine was equally active in these two tissues. Haloperidol increased the turnover rate of dopamine in striatum with doses that are relatively smaller than those required in the nucleus accumbens. Clozapine was more active in increasing turnover rate of dopamine in nucleus accumbens; the activity of chlorpromazine in these two tissues was equal. These results suggest that antipsychotics with high incidence of extrapyramidal side effects affect the nigrostriatal dopaminergic pathway selectively.

Cannabinoids: influence on neurotransmitter uptake in rat brain synaptosomes.

Abstract: We have examined the effect of Delta1-tetrahydrocannabinol (delat1-THC) and 12 of its derivatives on the uptake of 3H-labeled norepinephrine (NE), dopamine (DA), serotonin (5-HT) gamma-aminobutyric acid (GABA) into synaptosomes in homogenates of various regions of rat brain. Delta1-THC inhibits the accumulation of NE and 5-HT into hypothalamic preparations and DA into the corpus striatum with Ki values of about 12 to 25 muM while GABA uptake into cerebral cortical preparations is inhibited less (Ki = 140 muM). The affinities of delta6-THC, 7-hydroxy-delta1-THC, 7-hydroxy-delta6-THC and cannabidiol for 5-HT, NE and GABA transports are similar to values for delta1-THC, while cannabigerol, cannabinol and delta6-THC-7-oic acid have substantially less affinity. Thus, hydroxylation of C-7 in delta6-THC does not alter inhibitory potency, but its oxidation to an acid and aromatization of ring A greatly reduce affinity. The hydroxyl at C-3(1) of ring C is critical for inhibition of NE, 5-HT and GABA uptake, since its acetylation or methylation abolishes activity. Inhibition of NE, DA, 5-HT and GABA uptake by all cannabinoids examined is noncompetitive. Only about 1% of delta1-THC and delta6-THC and 5% of cannabidiol are fully soluble under our experimental conditions.

Disposition of naloxone: use of a new radioimmunoassay.

Abstract: Understanding of the pharmacology of the narcotic antagonist naloxone has been limited by the lack of a convenient and sensitive method of assay. A radioimmunoassay for naloxone has been developed and is described. It is applicable for drug analysis in either serum or brain. The limit of sensitivity of the assay was 0.1 ng. Naloxone glucuronide, noroxymorphone (nor-naloxone) and morphine were not recognized by the antibody whereas naltrexone and 6-hydroxynaloxone were able to displace naloxone-3H from the antibody. The assay was of sufficient sensitivity to follow the serum levels of naloxone in man for up to 2 hours after an i.v. injection of 0.4 mg. In animal studies, the biologic half-lives of naloxone or morphine (5 mg/kg) were compared after s.c. injection in rats. The peak serum levels A (1 mu/mo), time to peak serum levels (less than 1/2 hour), and serum half-life (40 minutes) were comparable. However, the brain entry and egress of the two compounds differed markedly. Peak brain levels of naloxone occurred within 15 minutes and had declined by 50% within 1 hour, whereas the peak brain levels of morphine were sustained for up to 2 hours. At peak serum levels, the brain/serum ratio for morphine was 0.1 whereas for naloxone it was 15 times greater. We suggest the high brain/serum ratio of naloxone contributes to its potency whereas the rapid egress from the brain is important in the short duration of action of naloxone.

Brain concentration of propranolol in relation to hypotensive effect in the rabbit with observations on brain propranolol levels in man.

Abstract: Intracerebroventricular (ICV) injection of propranolol in the dog, cat and rabbit produces a significant fall in arterial pressure. In the following experiments, regional brain propranolol concentrations and changes in mean arterial pressure (MAP) have been measured in the rabbit after central and peripheral administration of the drug and the results compared to human brain/plasma levels. In the conscious rabbit, ICV injection of l-propranolol (500 mug) produced a prolonged fall in MAP, maximal at 105 minutes (16.8 plus or minus 5.9 mm Hg below base line). The regional brain propranolol concentrations after ICV injection of 14C-dl-propranolol (530 mug) were determined and the levels compared to those achieved following i.v. infusion of the unlabeled drug (1.0 and 2.0 mg/kg/hr). The propranolol concentrations in the hypothalamus, medulla pons and midbrain after i.v. infusion were similar to the propranolol content in these areas at 60 and 120 minutes after ICV injection. Intravenous infusion of propranolol also resulted in significant falls in MAP between 60 and 120 minutes. In control studies, infusions of d-propranolol (1.0, 2.0 and 4.0 mg/kg/hr), which is virtually devoid of beta adrenoceptor blocking activity, produced only slight reductions in MAP. Postmortem studies in patients treated with prolonged i.v. infusions of d-propranolol as part of the treatment of paraquat poisoning indicate that the brain/plasma concentration of propranolol in man is similar to that observed in the rabbit. Propranolol is therefore highly concentrated in human brain tissue and comparable brain levels in the rabbit result in a hypotensive response.

Sex and estrogens and responsiveness of terminal arterioles to neurohypophyseal hormones and catecholamines.

Abstract: It has been generally assumed that reactivity (or responsiveness) of mammalian microcirculatory blood vessels to vasoactive hormones is not influenced by sex. In view of the paucity of knowledge in this area, the present in vivo studies were initiated to determine the quantitative dose-response relationships (by means of a high magnification image-splitting television microscope recording system) of catecholamines, selected sympathomimetics, neurohypophyseal hormones (NHPH), serotonin and angiotensin on mesenteric arterioles of unpretreated male and female rats and male rats pretreated with single low doses of 17 beta-estradiol (2 and 10 mug/100 g s.c.). The results indicate: 1) dose-response curves for the constrictor catecholamines (epinephrine and norepinephrine) and NHPH (vasopressin, oxytocin, vasotocin) in female rats are significantly shifted in parallel manner to the left of those obtained in male rats; 2) pretreatment of male rats with estrogen results in an enhancement of the constrictor actions of catecholamines, NHPH and phenylephrine; 3) the maximal arteriolar contractile responses (i.e., lumen narrowings) to norepinephrine and phenylphrine were enhanced by pretreatment with estrogen; and 4) dose-response curves for arteriolar constrictions induced by dopamine, serotonin or angiotensin were not affected by sex or estrogen pretreatment. The sex-linked differences, observed in this study, thus appear to be specific for NHPH and certain alpha adrenergic agonists. Overall, these findings reinforce the concept that sex hormones may play a role in control of peripheral blood flow and reactivity of arteriolar smooth muscle.

Actions of ricinoleic acid and structurally related fatty acids on the gastrointestinal tract. II. Effects on water and electrolyte absorption in vitro.

Abstract: Ricinoleic acid, the active component of castor oil, and related fatty acids were studied to determine their relative inhibitory effects on water and electrolyte absorption using everted hamster jejunal and ileal segments. Differences were found between hydroxylated and nonhydroxylated congeners as well as between cis and trans geometric isomers. At a mucosal concentration of 2.0 mM, the unsaturated fatty acids had the following rank order of potency on inhibition of water absorption: ricionoleate greater than or equal to ricinelaidate- greater than equal to linoleate greater than oleate greater than linelaidate greater than elaidate. Ricinoleyl alcohol was effective at 2.0 mM but the methyl ester of ricinoleic acid was ineffective at this concentration. Among a series of saturated fatty acids including palmitate, stearate, a mixture of 9- and 10-hydroxystearate, and 12-hydroxystearate, only the last compound had any inhibitory effect on water absorption. The results define those portions of the ricinoleic acid molecule required for its effect on water and electrolyte absorption and suggest that classification of this cathartic as an "irritant" or "stimulant" should be re-evlauated.

Regulation of cyclic adenosine 3',5'-monophosphate levels in guinea-pig cerebral cortex by interaction of alpha adrenergic and adenosine receptor activity.

Abstract: Direct assay of adenosine 3',5'-monophosphate (cyclic AMP) in guinea-pig cerebral cortex in vitro has shown that an alpha adrenergic receptor that was previously found to increase tissue content of cyclic AMP requires the co-presence of adenosine. This alpha adrenergic receptor complex was characterized with blocking agents and contrasted with other activities by examining the effect of other biogenic amines on cyclic AMP content in the presence of adenosine. Phentolamine (but not propranolol) reduced the potentiated response to norepinephrine (NE) (or epinephrine) plus adenosine to the level seen with adenosine alone. Theophylline, an adenosine antagonist, blocked the entire effect of NE plus adenosine. The failure of a high Mg++/Ca++ ratio to block the effect of NE plus adenosine argues against indirect mediation of the alpha receptor effect via the release of K+ or via an unknown neurohumoral agent. The complex variety of potentiative interactions between biogenic amines and adenosine is unique to brain. These interactions may be explained by the proposed existence of both independent and dependent receptors. The dependent receptors respond only to the co-presence of two or more neurohumoral agents. An alternative explanation would involve a compartmentally selective impairment of cyclic AMP degradation.

Effects of heroin and methadone on plasma cortisol and testosterone.

Abstract: Narcotic addicts self-administered heroin intravenously for 10 days under controlled research ward conditions and were subsequently detoxified with methadone for 7 days. Plasma testosterone levels decreased signifcantly when heroin dosage was between 45 and 65 mg/day contrasted to predrug base-line levels. Testosterone levels remained depressed during methadone withdrawal. No statistically significant changes in a.m. plasma cortisol levels were observed during both heroin acquisition and methadone withdrawal.

Effects of mercury on spermatogenesis studied by velocity sedimentation cell separation and serial mating.

Abstract: Recently the potential toxicity of environmental mercury has become a major concern. Human tissues contain mercury due to daily environmental exposure. Nearly all of the mercury contaminating food is in the form of methylmercury complexes, due to the biotransformation of inorganic mercury. This report compares the reproductive effects of methylmercury hydroxide and mercuric chloride in male mice. The mercuric compounds were administered intraperitoneally once at a dose of 1 mg/kg (based on Hg++ concentration), or spermatogenic cells were exposed in vitro to Hg+ concentrations ranging from 10(-3) to 10(-8)M. Spermatogenic cells were separated for biochemical studies using the velocity sedimentation technique, and in vivo serial mating was used to assess fertility. The effects of CH3Hg+ or Hg++ on the uptake of 3H-thymidine by spermatogonia, 3H-uridine by early elongated spermatids, and 3H-L-leucine by late elongated spermatids were studied. These in vitro experiments indicated that at 1-(-3) m CH2HgOH reduced thymidine incorporation by spermatogonia by 40%, uridine incorporation by elongated spermatids by 39% and L-leucine incorporation by late elongated spermatids by 40%. Results obtained with HgCl2 were similar but of lesser magnitude. In vivo administration of CH3HgOH and HgCl2 significantly inhibited the uptake of thymidine, uridine and L-leucine by their respective spermatogenic cells. Fertility profiles obtained from serial mating studies indicated that the primary effect of CH3HgOH was on spermatogonial cells, premeiotic spermatocytes and early elongated spermatids, with no apparent effect on spermatozoa in testis, peididymis or vas deferentia. HgCl2 also primarily affected spermatogonial and premeiotic cells, but the effect was less than that seen with CH3HgOH. Statistical analysis indicated significant antifertility effects. Inhibition of uptake of thymidine and uridine was well correlated with the functionality of these cells as reflected in the fertility profile, excep for L-leucine uptake. Mercury ion-induced antifertility effects at the dosage used in these experiments are reversible. Thus, these results suggest spermatogenic effects of methylmercury complexes which might have important health consequences in man.

Neurogenic release of purine compounds in blood vessels.

Abstract: The isolated thoracic aorta, ear artery and portal vein of the rabbit concentrated tritiated material on exposure to tritiated adenosine, adenine and its nucleotides. 3H-adenosine was transformed and retained predominantly as 3H-adenosine triphosphate in the portal vein and aortic adventitia, but to a lesser extent in the aortic medial or muscle layer. On transmural stimulation, portal vein and aortic adventitial strips pretreated with 3H-adenosine released tritiated material, which was recovered mainly as tritiated adenosine and nucleotides. Guanethidine abolished this release in the aortic adventitia and greatly diminished it in the portal vein. Both the release and vasodilation induced by transmural stimulation in the portal vein were abolished by tetrodotoxin. It is suggested that purine compounds are released locally within vascular walls from both the adrenergic and nonadrenergic nerves. The results are compatible with the view that adenosine triphosphate or a related compound may function as an inhibitory modulator in association with the adrenergic nerves and as a vasodilator transmitter of the non-adrenergic nerves in the portal vein.