Showing papers in "Journal of Pharmacology and Experimental Therapeutics in 1961"

The fate of h3-norepinephrine in animals

Abstract: The fate of H3-norepinephrine has been investigated after intravenous injection into animals. In cats, it distributes unequally in the various tissues examined; it is selectively taken up and retained by heart, spleen and adrenal gland. After H3-norepinephrine administration H3-normetanephrine is found in all tissues analyzed, but the individual concentrations vary considerably; it is retained by tissues to a lesser extent than H3-norepinephrine, except in skeletal muscle where more H3-normetanephrine is found after 2 hours than after 2 minutes. In the whole mouse H3-norepinephrine disappears rapidly at first, but then relatively slowly. H3-normetanephrine accounts for most of the H3-norepinephrine that disappears early in these experiments. The importance of binding as a mechanism for the inactivation of circulating catecholamines is emphasized, and it is shown to be quantitatively more important for norepinephrine than for epinephrine. Differences in the degree of binding explain why H3-norepinephrine disappears more slowly than H3-epinephrine from blood and from tissues.

Effect of drugs on the uptake and metabolism of h3-norepinephrine

Abstract: Tyramine, amphetamine, cocaine, chlorpromazine, imipramine, reserpine, guanethidine and Dibenzyline (phenoxybenzamine) markedly reduced the concentration of administered H 3 - norepinephrine in the heart, spleen and (except for guanethidine) adrenal gland. These drugs lowered the H 3 -catecholamine concentration to a moderate degree in the liver. Imipramine was the only drug that lowered the H 3 -catecholamine in the skeletal muscle. The level of H 3 - normetanephrine was decreased by all these drugs in heart and spleen and in some cases in the adrenal gland and liver. Tyramine, amphetamine, cocaine, chlorpromazine, imipramine, reserpine, guanethidine and Dibenzyline also elevated the plasma levels of administered H 3 -norepinephrine for the first 5 minutes. The plasma levels of H 3 -normetanephrine were also raised to varying degrees. These drugs appear to be acting by preventing the entry and/or the binding of H 3 -norepinephrine. The following drugs had no significant effect on the tissue and plasma concentration of H 3 - norepinephrine and H 3 -normetanephrine: Regitine (phentolamine), dichlorisoproterenol, TM 10 B, hexamethonium and ouabain. The catechol-O-methyl transferase inhibitor, pyrogallol, elevated the concentration of H 3 - norepinephrine in heart, spleen, liver and muscle but not the adrenal gland and plasma, and lowered the concentration of H 3 -normetanephrine in these tissues except the heart and spleen. Catron, a monoamine oxidase inhibitor, had no effect on the tissue levels of H 3 -norepinephrine in these tissues (except skeletal muscle) and elevated the concentration of H 3 - normetanephrine in all tissues.

Antiserotonin-antihistaminic properties of cyproheptadine

Abstract: The antihistaminic-antiserotonin actions of 1-methyl-4-(5 -dibenzo[a,e] cycloheptatrienylidine)-piperidine hydrochloride (cyproheptadine) have been demonstrated in several different experimental situations. Antihistaminic activity was revealed by a capacity to anutagonize the vasodepressor effects of histamine in the dog and by an ability to annul the signs of toxicity of aerosohized histamine in guinea pigs. The anuti-serotonin actions of cyproheptadine included an ability to block the vasopressor actions of serotonin in the anesthetized, ganglionic blocking agent treated dog, a capacity to block the spasmogenic effect of serotonin on the isolated rat uterus and an inhibitory effect of the swelling and edema produced by the local injection of serotonin in the hind feet of rats. The inhibitory action against similarly-induced egg white edema probably was related to the basic anti-serotonin actionu of the agent. The antihistaminic and/or antiserotonin actions of cyproheptadine were compared with similar properties of a variety of other agents, including lysergic acid diethylamide and other simple indole derivatives, chlorpromazine, ehlorpheniramine, pyrilamine, thenalidine, promethazine, trimeprazine, thenylpyramine and diphenhydramine. Under the conditions described for the various comparisons, the antihistaminic action equalled or exceeded that of chlorpheniramine and the antiserotonin activity approached, equalled or exceeded that of lysergic acid diethylamide. Since both of these latter agents are among the most active members of their respective pharmacologic classes, it was evident that cyproheptadine possesses both actions to a relatively high degree.

Methods for evaluating addiction liability. (A) "Attitude" of opiate addicts toward opiate-like drugs. (B) a short-term "direct" addiction test.

Abstract: A method has been developed for quantifying the "attitude" of addicts toward opiate-like drugs when administered in single or chronic dosages. Questionnaires were used which provided for independently prepared ratings by patients and observers. In single doses, the effects of weak morphine-like drugs were readily differentiated from those of a placebo by both patients and aides. After single doses, the ratings of patients and observers were in good agreement; however, observers gave higher ratings than patients particularly in the parameters of "feel drug," identification as "dope," and degree of "liking." Although potent opiates given chronically by the subcutaneous route were classified by both patients and observers in a comparable manner, those given orally were divergently described. Both patients and observers readily differentiated a placebo from weak morphine-like drugs. Patients discriminated between drugs and route of administration to a greater extent than did observers, and in a manner which corresponded better with abuse rates for heroin, morphine and codeine. However, before a statement can be made about the relative validity of patients9 and observers9 ratings, many more drugs must be evaluated by diverse routes of administration and employing a larger sample of the addict population. A short, "double-blind," direct addiction, cross-over procedure of 18 to 20 days is satisfactory for developing significant degrees of physical dependence in the case of morphine and codeine-like drugs, but additional studies are necessary to determine its reliability for assessing the degree of physical dependence induced by weak compounds and compounds in the methadone and meperidine series.

Reduction of carbon tetrachloride in vivo and reduction of carbon tetrachloride and chloroform in vitro by tissues and tissue constituents

Abstract: Small amounts of chloroform were identified in the expired air of dogs that had received carbon tetrachloride by inhalation. Carbon tetrachioride was reduced to chloroform in vitro by homogenates of mouse liver, heart, kidney, lung, brain, and skeletal muscle. The reduction was still carried out but to a lesser extent by liver heated to inactivate enzymes. The reduction of carbon tetrachloride in vitro was also carried out with cysteine, reduced glutathione, ascorbic acid, and cytochrome c. No methylene chloride could be detected in the expired air of dogs that had received chloroform. Chloroform was reduced to methylene chloride in vitro by mouse liver and by cysteine and ascorbic acid but much more slowly than carbon tetrachloride was reduced. Even though the replacement of chlorine by hydrogen in carbon tetrachloride and chloroform may occur only to a small extent in vivo, the reaction may have important consequences. It requires acquisition of two electrons from an out-side source. It is suggested that this acquisition of electrons, as well as other undemonstrated but conceivable reactions involving the free radical postulated to be formed by homolytic fission of the carbon-halogen bond, underlie the hepatotoxic effects of alkyl halides.

An unusual type of sympathetic ganglionic stimulant.

Abstract: The pharmacological properties of McN-A-343, 4-( m -chlorophenylcarbamoyloxy)-2-butynyl-trimethylammonium chloride, are described. This agent produced a small depressor response followed by a large pressor response in chloralose-anesthetized dogs or cats with doses as small as 8 µg/kg, i.v., and progressively greater pressor responses at large dose levels until maximal responses were observed at doses of 200 to 300 µg/kg, i.v. Such pressor activity was not reduced, but was usually augmented by C-6 and similar compounds, and was antagonized by Dibozane, an adrenergic blocking agent. Reserpine pretreatment antagonized the pressor but not the depressor action of McN-A-343. Bretylium treatment affected these responses in a manner qualitatively comparable to that observed with reserpine pretreatment. Increase in force of cardiac contraction and increase in cardiac rate due to McN-A-343 were blocked by bretylium. The depressor activity and, surprisingly, the pressor activity of this substance were selectively blocked by atropine. In an attempt to explain the nature of this blockade, it was shown that McN-A-343 caused contraction of the nictitating membrane when given intravenously. On this basis, the possibility was entertained that McN-A-343 might be a ganglionic stimulant. This was verified by the demonstration that the material caused a contraction of the nictitating membrane when injected intraarterially to the ganglion in small amounts and by the finding that the contraction was abolished by ganglionic extirpation, postganglionic section, or small amounts of atropine administered intraarterially to the ganglion. It was also concluded that sympathetic ganglionic stimulation was responsible for the observed pressor responses, since the pressor activity of McN-A-343 was abolished by bilateral sympathectomy and adrenalectomy. It was shown also that McN-A-343 was without detectable activity in isolated cat or rabbit hearts, and was less than 1/200 as active as ACh in producing contraction of isolated rabbit jejunal strips. Blood-flow experiments, carried out in the dog femoral bed, indicated that this material caused a direct penipheral dilator effect which was selectively antagonized by atropine. Although McN-A-343 was approximately as active as ACh in producing contracture of the isolated frog rectus muscle, it was found to be unable to produce a rapid twitch response in mammalian skeletal muscle when administered intraarterially, a response readily demonstrated with ACh. Contrary to expectations, nicotine was also found to be inactive in this respect. It is concluded that the pressor activity of McN-A-343 is due to ganglionic stimulation; furthermore, it appears to act selectively on sympathetic ganglia. Activation of cholinoceptive sites at vascular smooth muscle is probably the basis of the transient depressor response. Antagonism by atropine of the action of McN-A-343 at ganglionic sites indicates the presence of receptor areas or ganglion cells distinct from those which are selectively activated by ACh and blocked by C-6. Evidence presented here suggests that these receptor areas may be of physiological importance in the maintenance of sympathetic tonus.

The effects of alpha-methyl-DOPA and alpha-methyl-metatyrosine on the metabolism of norepinephrine and serotonin in vivo.

Abstract: α-Methyl-3-hydroxyphenylalanine and L-α-methyl-3,4-dihydroxyphenylalanine are decarboxylase inhibitors in vitro and in vivo . Both compounds deplete endogenous norepinephrine in brains and hearts and serotonin levels in the brains of rats and guinea pigs. Although the levels of serotonin return to normal in less than 24 hours, approximating the return to normal activity of the decarboxylation enzyme, the norepinephrine levels in the heart remain depressed for days longer. This study has shown that biosynthesis of norepinephrine can occur during this period and that the ability of the heart to hold norepinephrine is impaired. The prolonged depletion of norepinephrine for days after its precursor dopamine, and serotonin have returned to normal levels is clearly not related to inhibition of the decarboxylation enzyme. This report further demonstrates that the longlasting effect on norepinephrine is caused by the impairment of the tissues to hold the hormone.

Norepinephrine metabolism in rat brain and heart

Abstract: Previous studies by others have shown that norepinephrine is metabolized largely by two alternate enzymes: catechol-O-methyl transferase and monoamine oxidase. The present study was undertaken to evaluate which of these enzymes is of greater significance in the metabolism of norepinephrine in the brain and heart of the rat. Monoamine oxidase activity, measured in vitro, was found to be 3.6 and 5 times greater than catechol-O-methyl transferase activity in the brain and heart, respectively. However, in rat liver catechol-O-methyl transferase activity was 15 times greater than monoamine oxidase activity. A significant increase in the catecholamine content of rat brain and heart was produced by the intraperitoneal admimstration of four different monoamine oxidase inhibitors. The intraperitoneal injection of pyrogallol, an inhibitor of catechol-O-methyl transferase, failed to increase the catecholamine content of the brain or heart, even after 18 hours of enzyme inhibition. Norepinephrine was injected intravenously into rats, and the rate of disappearance of the amine from the plasma and heart was determined. In animals pretreated with iproniazid the major finding Was a marked accumulation of amine in the myocardium, relative to the concentration present in plasma; clearance of norepinephrine from the plasma was only moderately prolonged. Rats pretreated with pyrogallol, on the other hand, demonstrated a severe impairment in their ability to metabolize circulating norepinephrine. These experiments show that endogenous norepinephrine accumulates in the brain and heart of the rat when monoamine oxidase is inhibited; exogenous norepinephrine accumulates in the heart under the same conditions. Neither of these effects is produced by a catechol-O-methyl transferase inhibitor. The results suggest that oxidative deamination is the more significant pathway in the metabolism of norepinephrine in the brain and heart of the rat. This conclusion is quite compatible with the observation that O-methylation is the major pathway for circulating norepinephrine if one assumes that the liver participates in the metabolism of circulating amine. The liver is by far the richest source of COMT in the rat, and O-methylating activity in this organ greatly exceeds that of monoamine oxidase. Previous work by others, cited in the discussion, suggests that these findings may not necessarily apply to other species. The relative significance of these two metabolic pathways probably varies considerably from organ to organ and from species to species.

Analysis of the effects of changes in rate and rhythm upon myocardial contractility.

Abstract: During periods of quiescence the contractility of heart muiuscle approaches asymptotically a state characterized by the rested-state contraction. Activation of the muscle produces two temporary changes with opposing effects upon contractility. One tends to increase the strength of subsequent beats; it is responsible for the positive inotropic effect of activation (PIEA). The other tends to decrease the strength of following contractions and is manifest as the negative inotropic effect of activation (NIEA). The strength of a beat occurring at any given monuent is equal to that of the rested-state contraction, plus the cumulated PIEA, minus the cumulated NIEA. Changes in the absolute amounts of the PIEA and the NIEA account for the various changes in the strength of contraction that result from changes in the rate or rhythm of the heart. Both effects are operative in all homeothermic species investigated, but there are marked species differences in the relative prominence of the two and in the frequency ranges over which they are important. The intensity of the states responsible for the positive and negative inotropic effects of activation can be measured over a wide range by the resulting alterations in the strength of contraction. Changes in the intensity of the two states result from every beat whatever the frequency of contraction. Both states are capable of cumulation; the extent of cumulation depends on their respective rates of production and decay. Methods for the quantitative determination of these rates are described. The following observations account for the marked differences in the cumulation of the two effects at various frequencies of contraction: 1) each beat has a relatively small positive inotropic effect of activation, and the effect disappears slowly and exponentially; 2) each beat has a larger negative inotropic effect of activation which disappears rapidly in the period immediately following the beat, and then more slowly and exponentially; 3) the amounts of the PIEA and the NIEA produced per beat and the characteristics of the PIEA and NIEA decay curves are not necessarily independent of the interval between contractions. The positive and negative inotropic effects of activation reflect primarily changes in the force-velocity relationship rather than in the duration of the active state of the muscle.

The effect of adrenergic blocking agents on some metabolic actions of catecholamines

Abstract: Dichloroisoproterenol (DCI) has been shown previously to prevent both epinephrine-induced augmentation of contractile force and activation of phosphorylase in the dog heart in situ. The present investigation demonstrates that DCI almost completely abolishes the increase in blood glucose and free fatty acids produced by epinephrine, norepinephrine, and isoproterenol in the dog. The hyperlactic acidemic effect of epinephrine is partly blocked. On the other hand DCI does not block epinephrine-induced hyperglycemia in mice. In contrast to DCI, phenoxybenzamine interferes neither with the hyperglycemia nor the increase in blood lactic acid produced by epinephrine in the dog. Ergotamine antagonizes the hyperglycemia but not the hyperlactic acidemia. Phenoxybenzamine effectively blocks the vasopressor response to norepinephrine and epinephrine, and ergotamine produces maximal reversal of epinephrine. Neither of these drugs in the doses used antagonizes the positive inotropic effect of adrenergic stimuli. Both DCI and phenoxybenzamine increase blood glucose and lactic acid. High doses of DCI appear to antagonize the hyperglycemic action of low doses. The hyperglycemia and hyperlactic acidemia produced by phenoxybenzamine are antagonized by DCI. DCI also produces a marked and sustained increase in plasma free fatty acids even with doses which do not block this action of norepinephrine. The relationship of the drug-induced blockade of the metabolic actions of catecholamines with the other actions of adrenergic blocking agents is discussed. Possible mechanisms of actions and classification of adrenotropic receptors subserving the metabolic actions are considered.

Pharmacology of 2-amino-indane hydrochloride (su-8629): a potent non-narcotic analgesic

Abstract: Su-8629 (2-amino-indane) has oral analgesic potency and a therapeutic index comparable to morphine sulfate; it is unlike morphine in that it does not depress respiration and is not antagonized by nalorphine. In addition to its intrinsic analgesic effects, Su-8629, given in subthreshold doses, potentiates the analgesic effects of morphine, a property which it has in common with amphetamine. Su-8629, amphetamine and morphuine all afford protection against writhing induced by the intraperitoneal administration of acetic acid. The very marked increase in toxicity of amphetamine fouml in crowded mice as compared to isolated ones is not seen with Su-8629, nor does Su-8629 increase spontaneous motor activity as amphetamine does. On the other hand, Su-8629 and amphetamine, but not morphine, cause some elevation in electroshock threshold. Su-8629, amphetamine and morphine, when given in appropriate doses, reduce gastrointestinal motility of the mouse. Whereas morphine depresses respiration, blood pressure and spinal reflexes of intact chloraloseurethane anesthetized cats, Su-8629 and amphetamine in sufficiently high doses increase respiration, blood pressure and spinal reflexes. Su-8629 does not alter the blood sugar of the unanesthetized rabbit.

A comparative study of physiological and subjective effects of heroin and morphine administered intravenously in postaddicts

Abstract: Using a variety of subjective and objective measures, the relative potency of heroin to morphine administered intravenously to postaddicts found 1.80 to 2.66 mg of morphine sulfate equal to 1 mg of heroin. In addition, it was found that postaddicts could identify heroin and morphine as such with a high degree of accuracy when these agents were administered intravenously either on an acute or chronic basis. Though postaddicts showed no preference for one or the other of these drugs when administered on a single injection basis, five out of eight expressed a preference for heroin in the short-term addiction study. However, on the basis of postaddicts9 reports on "the most important effects of morphine and heroin," no constellation of effects could be discerned that explained the preference for heroin. Equipotent doses of these drugs had quite comparable action time courses when administered intravenously, and on this basis there was no marked difference in their ability to produce feelings of "euphoria," ambition, nervousness, relaxation, drowsiness, or sleepiness. Although the heroin abstinence syndrome was of shorter duration than that of morphine, the peak intensity was quite comparable for the two drugs. Data acquired during short-term addiction studies did not support the statement that tolerance develops more rapidly to heroin than to morphine. These findings have been discussed in relation to the physicochemical properties of heroin and morphine and the metabolism of heroin.

Effects of reserpine and cold-exposure on pittuitary-adrenocortical function in rats

Abstract: The effects of reserpine and cold-exposure have been compared on various indices of pituitary adrenal stimulation in rats: adrenal ascorbic acid, plasma corticosterone and FFA, and liver TPO. Both reserpineand cold-exposure elicita marked hypersecretion of ACTH. Of a number of Rauwolfia alkaloids, however, only those compounds which lowered brain stores of norepinephrine and serotonin and produced sedation, also evoked ACTH hypersecretion. A large dose of reserpine or a prolonged cold-exposure decreased the content of ACTH in the pituitary to suchan extent that the animals could not respond to an additional pituitary stimulus.

Effects of lsd-25 on brain serotonin

Abstract: LSD-25 in doses of 130 to 1300 µg/kg induced a small and significant rise in levels of rat brain serotonin within 10 to 120 minutes following administration. A single dose was as effective as several daily doses. In reserpine treated animals, LSD-25 induced a 2-fold elevation in brain serotonin, and effects were found 96 hours following a single dose of LSD-25. A dose-effect interaction of LSD-25 and reserpine was evident. Peripheral antiserotonin potency does not correlate with the effect on brain serotonin since the order of potency in elevating brain serotonin following reserpine induced depletion was: LSD-25, ALD-52, and BOL-148. With high-speed centrifugation the effects of LSD-25 on brain serotonin are largely in the particulate fraction. LSD-25 in vivo or in vitro did not increase the destruction of serotonin or change the net synthesis of serotonin from 2 X 10-4 M 5-hydroxytryptophan. These findings are interpreted as an effect of LSD-25 on inducing binding of brain serotonin and stimulating the binding of serotonin following reserpine induced depletion.

Modification of the effect of tyramine by various agents and procedures

Abstract: The modification by various substances of the dose-response curve of tyramine was studied in spinal cats; recorded were the nictitating membrane, the blood pressure and the heart rate. Pretreatment of short duration with reserpine (previously found to cause no supersensitivity to norepinephrine) reduced the effect of tyramine; the mode of action of reserpine was that typical for an "unsurmountable" antagonist. After pretreatment with reserpine the response of the nictitating membrane to tyramine was significantly related to the response of the nictitating membrane to nerve stimulation. The main effect of injections of increasing amounts of cocaine was a graded parallel shift of the dose-response curve of tyramine to the right; the mode of action was that typical for a "surmountable" antagonist. 2,6-Xylyl ether of choline (TM 10), morphine and methadone, given in amounts sufficient to reduce or abolish the response of the nictitating membrane to nerve stimulation, failed to reduce or abolish the response to tyramine. The phenomenon of subsensitivity to tyramine can be experimentally separated from that of supersensitivity to norepinephrine; it is likely that two different mechanisms are responsible for the two phenomena. The evidence is compatible with the view that tyramine liberates norepinephrine from tissue stores, and a scheme is discussed which accounts for the available evidence concerning norepinephrine storage sites.

The metabolism of drugs by liver microsomes from alloxan-diabetic rats

Abstract: Diabetes induced by alloxan affects certain hepatic microsomal drug-metabolizing enzymes. A depressed ability to metabolize drugs is evident in vitro, and sleeping times after hexobarbital are prolonged in vivo. The effects can be reversed by treating such diabetic animals with insulin. Insulin has no action in vitro, however. The decreased enzyme activity cannot be explained by a lack of TPNH, the presence of enzyme inhibitors, or a direct action of alloxan. A possible relation between hepatic levels of glycogen and drug-metabolizing enzyme activity is discussed. The proposal is made that factors leading to severe depletion of hepatic glycogen will probably affect the rate at which drugs are metabolized by the microsomes. Certain therapeutic implications are discussed.

A drug-induced change in the distribution and renal excretion of sulfonamides

Abstract: The distribution of certain sulfonamides in the rat can be modified by interfering with their binding to plasma protein by another drug. Of a wide variety of drugs tested, sulfinpyrazone, ethyl biscoumacetate and iophenoxic acid were found to be the most active in displacing a sulfonamide from albumin. Effective displacing agents in this system were acidic and highly bound to plasma. Other desirable structural characteristics were suggested on the basis of the drugs found to be active. The effect of the displacing agent in vivo appeared due to interference with the binding of the sulfonamide, since drugs active in vitro were the only ones active in vivo, and in the same relative order. The displacing agent altered the plasma and tissue concentrations only of those sulfonamides that showed more than 45% plasma binding. The net effect of displacement in vivo was a drop in plasma concentration of total drug and an increase in the unbound fraction, resulting in an increased concentration of sulfonamide (unbound) in tissue. The displacing agent used (sulfinpyrazone), being a strong organic acid (pKa 2.8) also competed for the renal secretion of those sulfonamides which were handled in this manner. The overall effect of sulfinpyrazone therefore was assessed on the basis of its effect on the kidney as well as its effect on plasma binding.

Some biochemical effects of alpha-methyl-3,4-dihydroxyphenylalanine and related compounds in mice.

Abstract: The 3-hydroxy, 2,3- and 3,4-dihydroxy derivatives of DL-α-methylphenylalanine, and the corresponding derivatives of DL-α- methylphenethylamine, have been tested in the mouse for their ability to: 1) inhibit dopa decarboxylase, 2) influence the concentration of serotonin in the brain, and 3) influence the concentration of norepinephrine in the brain and heart. The three amino acids were found to be decarboxylase inhibitors in vivo , the dihydroxy derivatives being more potent than the monohydroxy derivative. None of the amines in fluenced decarboxylation in vivo . Brain serotonin concentrations were definitely decreased by the 3-hydroxy and 3,4-dihydroxy amino acids, maximum effects being noted about 3 hours following i.p. administration of the drugs, and return to normal levels observed by 16 hours post injection. Measured 16 hours after drug administration, brain and heart norepinephrine was decreased by α-methyl-dopa, α-methyl-m-tyrosine and the corresponding amines with the exception that α-methyl-dopamine did not influence brain norepinephrine. In those cases where tissue norepinephrine was lowered, the effect was still discernible after 6 days. The ability of α-methyl-dopa to inhibit dopa decarboxylase and deplete tissues of norepinephrine resides solely in the L-isomer.

The development of supersensitivity to norepinephrine after pretreatment with reserpine

Abstract: In two series of spinal cats a study was made of the influence of pretreatment with reserpine on the sensitivity of the nictitating membrane to norepinephrine and on the depletion of the norepinephrine stores. An estimate of depletion was obtained by comparing the response of the nictitating membrane to continuous supra-maximal nerve stimulation (applied at various rates of stimulation) with its response to the continuous intravenous infusion of various amounts of norepinephrine. In the first series of experiments a single injection of various doses of reserpine (0.1 to 3.0 mg/kg) was given intraperitoneally 24 hr prior to the experiment. Depletion increased with the dose of reserpine, but no supersensitivity to norepinephine was observed. In the second series small doses of reserpine (0.1 mg/kg) were administered daily; depletion increased with time (and total dose) and super-sensitivity developed after 7 to 14 days. The depletion was not more pronounced than that obtained in the first series of experiments. Fourteen days of pretreatment with 0.03 mg/kg reserpine also caused supersensitivity, although depletion was not as pronounced. It is concluded that, as far as the nictitating membrane is concerned, time is essential for the development of supersensitivity to norepinephrine and that there is no direct relationship between depletion of the norepinephrine stores and supersensitivity to norepinephrine. Supersensitivity of the circulatory system and of the cardiac pacemaker was observed after smaller amounts of reserpine and after shorter periods of pretreatment. It is concluded that time is relatively less important for the development of supersensitivity of the cardiovascular system. In spinal cats pretreated with reserpine, cocaine was found to retain its ability to increase the sensitivity to norepinephrine.

The enzymic oxidation of tryptophan to 5-hydroxytryptophan in the biosynthesis of serotonin.

Abstract: The enzyme system catalyzing the hydroxylation of tryptophan to 5-hydroxytryptophan has been isolated from the particulate fraction of the intestinal mucosal cells of the rat and guinea pig. The hydroxylation reaction requires ascorbic acid or its analogs and Cu ++ for activity, appears to function anaerobically, and is inhibited by the soluble fraction of the intestinal mucosal cell.

Effects of meprobamate on operant behavior in rats.

Abstract: Schedules of positive reinforcement were used to test the effects of meprobamate on the behavior of rats. On an FR 50 schedule, meprobamate had effects only at neurotoxic doses. On other schedules (DRL 18 LH 3, VI 1½, FI 5), meprobamate increased response rates. The effects of meprobamate were compared with effects of mephenesin, phenobarbital, chlorpromazine, prochlorperazine, and d -amphetamine on the DRL 18 LH 3 and FR 50 schedules. Mephenesin, chlorpromazine, and prochlorperazine did not increase response rates on the DRL 18 LH 3 schedule. Although there were some similarities between the effects of meprobamate and the effects of phenobarbital and d -amphetamine, qualitative differences were described.

The physiological role of acetyl-cholinesterase (AChE) in sympathetic ganglia.

Abstract: The following four proposed roles for the acetylcholinesterase (AChE) of the superior cervical ganglion, where the localization of the enzyme is predominantly presynaptic, were studied: (1) limitation, temporally or spatially, of the transmitter action of acetylcholine (ACh) at the postsynaptic site, (2) hydrolysis of liberated ACh to provide an immediate source of choline for uptake and resynthesis to ACh by the terminals of the preganglionic fibers, (3) protection of the presynaptic nerve terminals against endogenously liberated ACh, and (4) prevention of the accumulation and action of ACh liberated during the resting state. Some of the findings reported previously by others which form the basis for the first proposal were confirmed. However, experiments designed to obtain more definitive evidence for this proposal and, particularly, to assess the degree of the intraganglionic spread of ACh were unsuccessful. No evidence was obtained to support the second proposal. Although the rate of failure of transmission produced by repetitive preganglionic stimulation was accelerated markedly by diisopropyl phosphorofluoridate (isoflurophate, DFP), the infusion of choline, over a wide range of concentrations, produced no antagonism of the failure of transmission either before or after DFP. Thus, it is suggested that the failure of transmission under these conditions was due to the accumulation of excessive concentrations of ACh rather than a temporary depletion of transmitter substance. Support for the third proposal was indicated by the findings that: (a) the mean threshold doses, for postganglionic activation, of carbachol were significantly (26-fold) higher in chronically denervated than in normal ganglia, and (b) although the mean threshold doses of ACh were the same in untreated denervated and normal ganglia, after DFP the thresholds were significantly (5-fold) lower in the latter as compared with the former. The mean threshold dose of ACh was 10 times that of carbachol in normal ganglia; however, in the three situations where AChE was inactivated or absent ( i.e., denervated ganglia before and after DFP, and normal ganglia after DFP), the mean threshold doses of ACh were only one-third to one-half those of carbachol. A limited number of similar experiments was conducted with butyrylcholine and tetramethylammonium. It is inferred from these observations that in normally innervated ganglia, threshold doses of carbachol, and possibly of ACh, activate only the presynaptic terminals, causing them in turn to liberate the neurohumoral transmitter, with consequent activation of the postsynaptic site. Hence, it is suggested that the primary role of ganglionic AChE is the limitation of the action of liberated ACh on the presynaptic nerve terminals themselves. Other possible interpretations are also considered. It was observed also that in denervated ganglia the mean threshold doses of both ACh and carbachol were reduced by DFP to the same extent. The possibilities that the butyrocholinesterase of the capsular glial cells, or some nonspecific group at the receptor site, plays a role in the potentiation of these agents by DFP are discussed. The finding that persistent asynchronous postganglionic firing occurred in acutely decentralized resting ganglia following the injection of larger doses of DFP provides support for the last proposal. Postganglionic firing following massive doses of DFP did not occur in chronically denervated ganglia.

Accumulation of epinephrine and norepinephrine by some rat tissues

Abstract: Tissue handling of catecholamines has been investigated on the basis of determinations of tissue levels in rat hearts and salivary glands. Bilateral suprarenal demedullation did not alter the tissue levels. Chronic superior cervical gan glionectomy led to the disappearance of norepinephrime but not of epinephrine from the salivary glands. Combining these two procedures resulted in disappearance of both amimes. Injection of epinephrine or norepinephrine into demedullated animals caused a marked increase in the content of the corresponding amine in the heart and salivary glands and a decrease in the concentration of the other, indicating decreased synthesis, or more probably, displacement of endogenous catecholamine. Most of the increase in salivary glands following injection was prevented by chronic superior cervical ganglionectomy, which limited the catecholamine content to the equivalent of the epinephrine level in denervated glands from animals with intact suprarenals. It is concluded that epinephrine and norepinephrine can be accumulated from the bloodstream and stored in tissues other than those in which they were synthesized. Most of the accumulation is in tissue sympathetic nerve endings, which have a storage capacity considerably greater than their normal catecholamine content. Quantitative aspects of this uptake suggest that it may play an important role in terminating the actions of exogenous and particularly those of endogenous catecholamines.

Influence of chlorpromazine and chlorprothixene on the cerebral metabolism of 5-hydroxytryptamine, norepinephrine and dopamine.

Abstract: In rat brain chlorpromazine and chlorprothixene did not affect the content of endogenous 5-hydroxytryptamine (5HT), dopamine (3-hydroxytyramine, DA) and norepinephrine (NE). However, the drugs counteracted the following changes in the monoamine content: 1) release of 5HT, DA and NE after administration of reserpine, 2) increase of 5HT, NE (but not of DA) after administration of MAO inhibitors of the hydrazine type, 3) increase of 5HT after injection of 5-hydroxytryptophan (5HTP). Since chlorpromazine inhibits neither monoamine oxidase (MAO) nor decarboxylase of aromatic amino acids (DCO) nor the penetration of MAO inhibitors into the brain, it is suggested that chlorpromazine and chlorprothixene may act by decreasing the permeability of the storage organelles for some monoamines.

The effect of obstructive jaundice on drug metabolism in rabbits

Abstract: Obstructive jaundice affects liver microsomal drug metabolism in rough proportion to the degree of histologically observable cell damage. Livers with mild cellular damage often retain essentially normal hexobarbital metabolism while other pathways are markedly reduced from normal levels. Severe cellular damage leads to nearly complete loss of all the drug enzyme activities studied. In vitro, sodium deoxycholate inhibits most drug enzyme activities at about the same final concentration—50% inhibition at approximately 1 x 10-2 M. The curves of enzyme inhibition and those of microsomal solubilization (Palade and Siekevitz, 1956) by deoxycholate can almost be superimposed on one another. This suggests that the two phenomena may be related. Deoxycholate effects on drug metabolism cannot be reversed by dialysis of the enzyme-bile acid mixture against distilled water. This too would be consistent with an inhibition-by-destruction mechanism. The prolongation of sleeping times seen when jaundiced and normal rabbits are compared is compatible with the effects of deoxycholate on the drug enzyme systems in vitro.

Effect of stress and tranquilization on plasma free fatty acid levels in the rat.

Abstract: Female albino rats were subjected to an anxiety provoking stress induced by irregular unavoidable electric shocking for periods of ½ to 7 hours. Plasma free fatty acid (FFA) concentrations rose to levels significantly above normal, the longer the period of stress, the greater being the rise. Rats receiving the tranquilizer chlorpromazine or meprobamate, and subjected to the stress for 4 hours, manifested either smaller or no rises in plasma FFA, depending upon the dose and time of drug administration, in contrast to control animals not receiving a drug. It is concluded that it is possible to inhibit the FFA response to stress by affecting the central nervous system with tranquilizing drugs as well as by inhibiting peripheral autonomic stimulation of fatty depots.

Demonstration of tolerance and physical dependence in the dog following a short-term infusion of morphine

Abstract: An 8-hour infusion of morphine has been used to produce a demonstrable degree of physical dependence and tolerance in the dog. Physical dependence has been unmasked by nalorphine and the syndrome produced by this procedure is distinct, reproducible, and consists of restlessness, apprehension, violent tremors, lacrimation, salivation, rhinorrhea, urination, defecation, vomiting, mydriasis and tachycardia. Tolerance is readily discernible during the course of infusion and can be clearly demonstrated the day following infusion, using a standard test dose of morphine. Tolerance to behavioral depression (narcosis), depression of the skin twitch, and withdrawal reflex is marked. The reproducibility and brevity of this method may recommend it for preliminary screening of analgesic agents to identify those that produce physical dependence.

Inhibition of adrenergic cardiac acceleration by cardiac glycosides.

Abstract: In anesthetized dogs with the heart denervated the cardiac glycosides, digitoxin and acetyldigitoxin, reduced the chronotropic response of the S-A and A-V nodes to epinephrine and to sympathetic nerve stimulation. This conclusion emerges from the following facts: (1) In doses greater than 30% of the lethal dose the glycosides invariably reduced the positive chronotropic response to epinephrine. The epinephrine dose-response curves obtained in the presence of digitalis fell below the control curves. In each experiment, if the ordinate values of the curve obtained after the administration of digitalis were multiplied by a constant, the resulting values coincided with the control curve. The inhibitory action of the cardiac glycosides was proportional to the dose employed. (2) The results obtained with sympathetic nerve stimulation were in every way similar to those obtained with epinephrine. It was concluded that digitoxin and acetyldigitoxin diminished the reactivity of the S-A and A-V nodes to the chronotropic action of epinephrine and of sympathetic stimulation.

Release of pharmacologically active substances from the rat skin in vivo following thermal injury

Abstract: By using suitable biological assays (guinea pig ileum, rat uterus, hen9s rectal cecum, rat9s blood pressure, and rat9s duodenum) evidence is presented to indicate that histamine, bradykinin, and adenyl compounds (adenosine and/or adenylic acid) appear in the wash fluid from the rat9s dorsal subcutaneous air pockets after immersing the outer skin in a water bath at 96°C for 15 seconds. Similar results were obtained when the air pocket was perfused and the skin burned by a 250-watt infrared lamp. There was a good parallelism between the amounts of histamine released under diverse conditions and the amount of bradykinin released. Diffusates into the fluid of the air pockets after burning were freeze-dried and fractionated by dialysis and 80% ethanol precipitation. The ethanol precipitate, which was more or less free of histamine and bradykinin when tested on the rat9s blood pressure and the hen9s rectal cecum, presented a discrepancy which suggested that the material present differed somewhat from adenosine. No direct examination for serotonin was made but indirect evidence was suggestive but not conclusive.

Inhibition of h3-norepinephrine release by monoamine oxidase inhibitors

Abstract: After the intravenous administration of H3-norepinephrine, it was taken up by the heart and slowly released over a period of days. Long-acting monoamine oxidase inhibitors blocked the slow release of H3-norepinephrine. Long-acting and short-acting monoamine oxidase inhibitors blocked the releasing action of reserpine on H3-norepinephrine in the heart. On the basis of these observations it is proposed that monoamine oxidase inhibitors elevated the catecholamine concentration in certain tissues by blocking the release of the hormone from its binding site.