Showing papers in "Pharmacology, Biochemistry and Behavior in 1974"
TL;DR: carry-over of both the post-injection augmentation and dark phase reduction of locomotion was revealed during amphetamine retest 8 days following discontinuation of daily d-amphetamine injections, indicating the importance of their concurrent evaluation, especially during chronic studies.
Abstract: The competitive relationship between d-amphetamine induced stereotypy and locomotor activity indicates the importance of their concurrent evaluation, especially during chronic studies. Repeated injection of 0.5, 1.0, 2.5, 5.0, or 7.5 mg/kg d-amphetamine for 36 successive days, in rats continuously exposed to the experimental chambers, produced a progressive augmentation in stereotypy and/or locomotion (depending on dose) during the 3–4 hr interval following injections (post-injection phase). In contrast, dark phase locomotor activity (8–20 hr after each daily injection) was maximally reduced (30–40% of controls) after the first injection of either 5.0 or 7.5 mg/kg d-amphetamine and gradually declined to this level with repeated injection of 1.0 and 2.5 mg/kg. Carry-over of both the post-injection augmentation and dark phase reduction of locomotion was revealed during amphetamine retest 8 days following discontinuation of daily d-amphetamine injections. Possible mechanisms underlying these behavioral alterations are discussed.
594 citations
TL;DR: The combination used here depresses REM sleep by about one half but does not reduce non-REM sleep, and the smaller the platform relative to the size of the rat, the greater the reduction in REM sleep - but at one point, non- REM sleep is decreased.
Abstract: This technique of REM sleep deprivation may make data interpretation difficult because it can lack selectivity, and because controls may suppress some REM sleep. To correct these difficulties, EEG recordings were made of rats placed in 4 situations for 96 hours: (1) baseline, (2) on 6.5 cm, or (3) 12.5 cm inverted flowerpots surrounded by water, (4) swimming in 10 cm water for 1 hr per 24 hr. Rats on the 6.5 cm pots had 57% as much REM sleep as baseline with no change in non-REM sleep. Rats on 12.5 cm pots initially had 55% as much REM sleep baseline, but by the fourth day increased to baseline levels. The swimming rats had no reduction in REM or non-REM sleep at any time, and thus seem to be a better control. The smaller the platform relative to the size of the rat, the greater the reduction in REM sleep - but at one point, non-REM sleep is decreased. The combination used here depresses REM sleep by about one half but does not reduce non-REM sleep.
257 citations
TL;DR: A technique is described which allows long term intravenous and intragastric infusions in rats and a new double lumen waterlight swivel is described for double infusions or infusion and sample experiments.
Abstract: A technique is described which allows long term intravenous and intragastric infusions in rats; the advantages of these methods is discussed. A new double lumen waterlight swivel is described for double infusions or infusion and sample experiments. Using the ensemble, rats have been infused for up to five months while at complete liberty of movement.
156 citations
TL;DR: The results suggest that the nigro-neostriatal dopaminergic projection may play an important role in the acquisition of learned instrumental responses.
Abstract: Rats subjected to bilateral injections of 6-hydroxydopamine (8 μg) into the zona compacta of the substantia nigra completely failed to learn either a one-way active avoidance response or a simple approach response for food reinforcement. The neurotoxic lesions reduced striatal dopamine and tyrosine hydroxylase activity to less than 10 percent of control levels. A significant loss of hypothalamic norepinephrine was also produced by these lesions suggesting that this procedure also destroyed part of the ventral noradrenergic bundle. When bilateral lesions of the latter pathway were made caudal to the substantia nigra, so that similar losses were produced in hypothalamic norepinephrine levels without reducing striatal tyrosine hydroxylase activity, normal acquisition of both avoidance and appetitive responses were observed. In another experiment, almost complete retention of avoidance responding was obtained if the animals were overtrained on this response prior to the bilateral nigral lesions. These results suggest that the nigro-neostriatal dopaminergic projection may play an important role in the acquisition of learned instrumental responses.
149 citations
TL;DR: R Rats with jugular cannulas self-administer the dopamine receptor stimulant apomorphine at doses from 0.125 to 1 mg/kg/injection, supporting the idea that the activation of dopamine receptors yields positive reinforcement.
Abstract: Rats with jugular cannulas self-administer the dopamine receptor stimulant apomorphine at doses from 0.125 to 1 mg/kg/injection. Pretreatment with the dopamine receptor blocker pimozide (0.5 or 1 mg/kg) disrupted the self-injection of apomorphine. These data support the idea that the activation of dopamine receptors yields positive reinforcement, although other neurochemical actions of apomorphine have not been ruled out. Dopaminergic mechanisms may also be involved in the self-administration of psychomotor stimulants and narcotics.
147 citations
TL;DR: ACTH 4–10 served to improve visual memory, decrease anxiety, reinstitute a previously habituated alpha blocking response in the occipital EEG, and generally influence the occIPital EEG toward a pattern consistent with increased attention.
Abstract: The effects of two polypeptides, ACTH 1–24 and ACTH 4–10 on a variety of bioelectric and behavioral measures of attention, memory and anxiety in human subjects were examined within the context of a disjunctive reaction time paradigm. ACTH 1–24 had no effect on any of the measures involved; ACTH 4–10 , however, served to improve visual memory, decrease anxiety, reinstitute a previously habituated alpha blocking response in the occipital EEG, and generally influence the occipital EEG toward a pattern consistent with increased attention. The results were taken to suggest a direct polypeptide influence on CNS attentional mechanisms.
141 citations
TL;DR: After training on a multiple FR-1FR-1 cocaine reinforcement schedule, responses were extinguished in one component of the schedule, and responses declined to near-zero levels within 4 sessions for 3 of 4 monkeys.
Abstract: After training on a multiple FR-1 FR-1 cocaine reinforcement schedule, responses were extinguished in one component of the schedule. Extinction responses declined to near-zero levels within 4 sessions for 3 of 4 monkeys. Response rate during the non-extinction component increased for a time in 2 of 3 animals exposed to prolonged extinction sessions. Three monkeys were then retrained to the multiple FR-1 FR-1 reinforcement schedule, after which each response in one component was followed by a brief electric shock as well as a cocaine infusion. Shocked responses decreased as shock intensity increased. Non-shocked response rates increased in a few sessions but this effect was transitory. Doubling the unit dose reduced baseline rate but failed to alter the relative suppressant effect of shock. Attenuation to intense shock occured when the response-shock interval was increased to 18 sec.
109 citations
TL;DR: Apomorphine and a combination of Ro 4-4602 with L-DOPA increase the copulatory behavior of male adult rats with a low basal level of sexual activity and this effect is prevented by haloperidol.
Abstract: Apomorphine and a combination of Ro 4-4602 with L-DOPA increase the copulatory behavior of male adult rats with a low basal level of sexual activity. This effect is prevented by haloperidol. This drug also suppresses the spontaneous copulatory behavior in rats with high basal level of sexual activity.
101 citations
TL;DR: Ethanol intake was greater when the rats were food deprived, but under both food conditions; this finding strengthened the conclusion that this concentration can serve as a reinforcer for the food-satiated rat.
Abstract: Ethanol intake and responding of 6 male albino rats were measured at concentrations of 0 (water control) 2, 4, 8, 16, and 32% (W/V) during daily 1-hr sessions in operant conditioning chambers. The rats were run first food deprived (80% of free-feeding weight) and then food satiated (free access to food in home cages). Ethanol intake was greater when the rats were food deprived, but under both food conditions: (1) ethanol intake exceeded that of water at all concentrations, (2) quantity (mg) consumed increased with the concentration, and (3) the highest rate of responding occured at the beginning of the session. In a second experiment, fixed-ratio responding maintained by contingent presentation of 32% (W/V) ethanol exceeded water control responding. This finding strengthened the conclusion that this concentration can serve as a reinforcer for the food-satiated rat.
92 citations
TL;DR: The results suggest that most psychomotor stimulants, although having different structures, are likely to produce discriminative stimulus properties similar to d-amphetamine.
Abstract: The discriminative stimulus properties of amphetamine were demonstrated in rats trained to discriminate between 0.8 mg/kg of d-amphetamine sulfate and saline. During the discriminative training, animals were shaped on a DRL 15-second schedule to respond to one of two levers for a food reward when they were given d-amphetamine, and to respond to the other lever when they were treated with saline. Tests for the discriminative stimulus properties consisted of 10-min extinction sessions in which the reinforcement delivery was disconnected. Animals receiving low doses (0.2–0.4 mg/kg) of d-amphetamine exhibited mostly saline-like responses, but at a dose of 0.8 mg/kg they produced more than 80% responses on the amphetamine lever. Doses higher than 2.4 mg/kg caused an initial stereotyped behavior and the animals showed a period of latency before responding on the amphetamine lever. In order to elucidate the structural characteristics of d-amphetamine involved in the production of the discriminative stimulus properties, a number of amphetamine derivatives and related compounds were administered to these animals. 1-Amphetamine, ephedrine, norephedrine, 4-methoxyamphetamine and methylphenidate all produced the discriminative stimulus properties similar to d-amphetamine, but doses of 2–10 times greater than d-amphetamine were necessary. Mescaline, STP and DOET did not produce the d-amphetamine-like responses. These results suggest that most psychomotor stimulants, although having different structures, are likely to produce discriminative stimulus properties similar to d-amphetamine.
91 citations
TL;DR: When both arousal and self- Stimulation are measured, it is found that noradrenaline is less specifically involved in self-stimulation than dopamine.
Abstract: Attenuation of self-stimulation produced by blockade of noradrenaline receptors (phentolamine) or inhibition of noradrenaline synthesis (disulfiram) was associated with sedation (defined by decreased locomotor activity and decreased rearing) in rats. Attenuation of self-stimulation produced by blockade of dopamine receptors was associated with only minor sedation. Thus when both arousal and self-stimulation are measured, it is found that noradrenaline is less specifically involved in self-stimulation than dopamine. The noradrenergic theory of reward cannot be accepted until it is shown that noradrenaline has an effect on reward aspects of self-stimulation independently of its general effects on behavior measured here by locomotor activity and rearing.
TL;DR: A functional—anatomical differentiation of dopamine pathways in brain is suggested through factor analysis of behavioral and biochemical data that suggested that only striatal dopamine content bore a high relationship to avoidance behavior, while ingestive behavioral measures were highly related to both striatal and limbic dopamine content.
Abstract: Alterations of shuttle-box avoidance acquisition, ingestive behavior, and catecholamine content in 4 different parts of brain were determined following bilateral infusion of 6-hydroxydopamine into the ventral tegmental area containing A-10 dopamine cell bodies, the tegmental segment of the ascending norepinephrine pathways, the globus pallidum, or the caudate-putamen The maximum antagonism of active avoidance acquisition occurred following placement of 6-hydroxydopamine into the ventral tegmental and caudate areas No effect on either avoidance or ingestive behavioral measures occurred after infusion of 6-hydroxydopamine into the norepinephrine pathways Factor analysis of behavioral and biochemical data suggested that only striatal dopamine content bore a high relationship to avoidance behavior, while ingestive behavioral measures were highly related to both striatal and limbic dopamine content Results suggest a functional—anatomical differentiation of dopamine pathways in brain
TL;DR: It was concluded that rats may learn the association between alcohol and relief of withdrawal symptoms, but a number of withdrawal episodes are required.
Abstract: The experiment examined the effects of single and multiple episodes of forced administration of a liquid diet containing ethanol on subsequent volitional ethanol consumption. Rats were subjected to a series of 3 sequences of forced liquid diet consumption lasting 20, 50 and 50 days. One group (AD) received a liquid diet with 35–42% of the calories in the form of ethanol. Another group (SD) received identical diets except sucrose was isocalorically substituted for ethanol. Following each sequence a free-choice test was given in which the rats were allowed to choose between an alcohol diet, a sucrose diet and water. After 20 days of alcohol consumption, rats in the AD group rejected the alcohol diet, despite the occurrence of severe withdrawal symptoms including tail-stiffening, ataxia, tremors and hyperreactivity. During subsequent preference tests, a substantial, but transient, increase in alcohol self-selection was observed. It was concluded that rats may learn the association between alcohol and relief of withdrawal symptoms, but a number of withdrawal episodes are required.
TL;DR: It is hypothesized that this reduction in sensitivity is one mechanism underlying the development of behavioral tolerance to DFP, but that muscarinic receptors may be more labile than nicotinic receptors.
Abstract: Effects of various cholinergic agents on the free operant responding and single alternation behavior of rats were examined following two regimens of chronic treatment with diisopropylfluorophosphate (DFP), an irreversible anticholinesterase, which lowered brain cholinesterase to 45% and 30% of normal, respectively. Reduction to 45% produced no observable changes in behavior; reduction to 30% gave rise to a decrease in the number of reinforced responses and an increase in the number of nonreinforced responses. Tolerance for the former measure developed within 10 days, whereas tolerance for the latter was not observed. Subsequent challenges were carried out using anticholinesterase agents, and muscarinic and nicotinic agonists and antagonists. The results suggest that the sensitivity og both muscarinic and nicotinic receptors to acetylcholine may be reduced during chronic treatment with DFP, but that muscarinic receptors may be more labile than nicotinic receptors. It is hypothesized that this reduction in sensitivity is one mechanism underlying the development of behavioral tolerance to DFP.
TL;DR: The lesion of brain serotoninergic pathways decreases both 5-hydroxytryptamine and 5-Hydroxyindolacetic acid levels in the forebrain and completely abolishes the aggressive behavior in previously fully aggressive mice.
Abstract: A decrease of brain 5-hydroxytryptamine turnover was described to be present in mice made aggressive by prolonged isolation. The lesion of brain serotoninergic pathways decreases both 5-hydroxytryptamine and 5-hydroxyindolacetic acid levels in the forebrain and completely abolishes the aggressive behavior in previously fully aggressive mice. No change of aggressive behavior or of serotonin levels was observed in aggressive mice submitted to lesions of other areas.
TL;DR: It was found that stress of inescapable unavoidable shock produced increased self selection of alcohol, and factors such as predictability of shock, shock schedule and nutritional deficiency were found not to alter alcohol consumption substanially.
Abstract: In five experiments it was found that stress of inescapable unavoidable shock produced increased self selection of alcohol. These effects were maintained only so long as the shock schedule was continued. Factors such as predictability of shock, shock schedule and nutritional deficiency were found not to alter alcohol consumption substanially. In contrast to the effects of inescapble unavoidable stress, shock-produced conflict did not lead tio the self selection of alcohol. Results were interpreted in terms of a Tension Reduction Hyothesis and the role of control over aversive stimulation.
TL;DR: Melanocyte stimulating hormone release-inhibiting factor (MIF), thyrotropin releasing hormone (TRH) and angiotensin II, injected i.p. to mice potentiate the behavioral effect of L-DOPA and 5-hydroxytryptophan.
Abstract: Melanocyte stimulating hormone release-inhibiting factor (MIF), thyrotropin releasing hormone (TRH) and angiotensin II, injected i.p. to mice, potentiate the behavioral effect of L-DOPA and 5-hydroxytryptophan.
TL;DR: Implantation of crystalline insulin in the hypothalamic ventromedial nucleus resulted in significant reduction of food intake in both normal and diabetic rats and was discussed in terms of the glucostatic theory of food intale regulation.
Abstract: This study reports the influence of insulin on food consumption in rats as mediated by ventromedial hypothalamic glucoreceptors. Implantation of crystalline insulin in the hypothalamic ventromedial nucleus resulted in significant reduction of food intake in both normal and diabetic rats. Administration of polyleucine or polyglycine caused no change in food intake. These results are discussed in terms of the glucostatic theory of food intale regulation.
TL;DR: While the midbrain raphe appears to be involved in the regulation of water intake and some behavioral responses to painful stimuli, lesions in these nuclei and reduction of telencephalic 5-HT are not sufficient to block morphine analgesia.
Abstract: Rats with lesions in the median raphe nucleus (MR group) or in both the dorsal and median raphe nuclei (R group) were compared with operated control animals on the following measures: telencephalic serotonin (5-HT) concentration; daily water consumption; acquisition of a two-way conditioned avoidance response; and morphine analgesia. Both lesions produced significant reductions in telencephalic 5-HT, reaching 33% in the MR group and 57% in the R group. Transient increases in water intake were observed in both groups, being more prolonged and of greater magnitude in the R group. On the other hand, facilitated shuttlebox avoidance learning was observed only in the R group. Neither lesion affected pain sensitivity or morphine (3–9 mg/kg) analgesia as measured by the hot-plate technique. Therefore, while the midbrain raphe appears to be involved in the regulation of water intake and some behavioral responses to painful stimuli, lesions in these nuclei and reduction of telencephalic 5-HT are not sufficient to block morphine analgesia.
TL;DR: The results of 2 non-contingent control groups indicated that mice injected with cycloheximide but given foot shock in a place different from the training apparatus did not show increased latency following treatment with catron and pargyline, indicating that recovery is specific for training in the passive avoidance task.
Abstract: Amnesia was induced in C57BL6J male mice by pre-training injections of cycloheximide (CYC) in a one-trial passive avoidance task. This amnesia was reversed by pre-testing injections of two monoamine oxidase inhibitors (MAOI's) catron and pargyline. The results of 2 non-contingent control groups indicated that mice injected with cycloheximide but given foot shock in a place different from the training apparatus did not show increased latency following treatment with catron and pargyline. This indicates that recovery is specific for training in the passive avoidance task. Depletion of norepinephrine (NE) by diethyldithiocarbamate (DEDTC), a dopamine beta hydroxylase inhibitor, resulted in an amnesia similar to that induced by CYC. DEDTC-induced amnesia was also reversed by catron and pargyline.
TL;DR: The results support the concept of the CNS actions of peptides in mice pretreated with GH-RIH, and show significant potentiation of the behavioral effects of DOPA.
Abstract: Significant potentiation of the behavioral effects of DOPA were observed in mice pretreated with GH-RIH. In addition, a slight reduction of oxotremorine induced symptoms was seen. No significant effects of GH-RIH were observed in several other tests involving the central nervous system (CNS). The results support our concept of the CNS actions of peptides.
TL;DR: The hypothesis that dopaminergic components of the striatum may be involved in avoidance behavior is supported by the results of this study.
Abstract: Bilateral administrations of crystalline 6-hydroxydopamine to the ventral anterior striatum of rats reliably impaired the performance of avoidance responses. The 6-OHDA treatments depleted the forebrain of dopamine but did not reliably alter forebrain levels of norepinephrine. A significant correlation was found between the extent of the depletion of forebrain dopamine and the magnitude of the avoidance deficit. These results support the hypothesis that dopaminergic components of the striatum may be involved in avoidance behavior.
TL;DR: Tolerance developed to the physiologically and behaviorally toxic effects of the drug over a six to ten month period over the course of this chronic administration of d-methamphetamine HCl in the rhesus monkey.
Abstract: The effects of the chronic administration of methamphetamine on food- and water-reinforced responding were investigated in the rhesus monkey. These animals received one infusion of d-methamphetamine HCl every three hours, eight times daily in doses starting at 0.0625 mg/kg/infusion and gradually increasing to 6.5 mg/kg/infusion. The effects of this drug regimen on food- and water-reinforced behavior generated by independent fixed-ratio 10 schedules of reinforcement were studied. Tolerance developed to the physiologically and behaviorally toxic effects of the drug over a six to ten month period. Gross morphological changes were not seen at necropsy nor during examination of brain, heart, liver or kidney tissue under light microscopy.
TL;DR: The results indicate that 5-HT has a facilitatory effect on the reflex and suggest that a catecholaminergic system is also involved in determining reflex amplitude, which is also suggested in the case of the reserpinized animal.
Abstract: The present investigation provides evidence for serotonergic involvement in the inhibition of the acoustic startle reaction which results from the presentation of neutral stimuli (prepulses) shortly before reflex elicitation. While the specific serotonin (5-HT) synthesis inhibitor p-Chlorophenylalanine did not affect the response, a large amine-depleting dose of reserpine enhanced the reaction elicited under stable (control) stimulus conditions (no prepulse delivered). Selective replacement of 5-HT by administration of the l -amino acid precursor and a monoamine oxidase inhibitor further enhanced control startle amplitude and also eliminated prepulse inhibition. Chemical assays indicated especially large increases in 5-HT levels in the cortex and brainstem. Administration of the 5-HT precursor in the non-reserpinized rat both increased control startle levels and also interfered with prepulse inhibition although not as completely as in the reserpinized animal. The results indicate that 5-HT has a facilitatory effect on the reflex and suggest that a catecholaminergic system is also involved in determining reflex amplitude.
TL;DR: It was suggested that the taste aversion behavior represented a conditioned anorexic effect rather than being indicative of a noxious or aversive consequence of the amphetamine, and may be mediated by a dopaminergic system.
Abstract: A comparison of the effects in rats of four dose levels of d- and 1-amphetamine (0.5, 1.0, 2.0 and 4.0 mg/kg) on development of a taste aversion to a 0.1% saccharin solution showed that d-amphetamine was approximately 4 times as potent as 1-amphetamine in inducing a taste aversion to saccharin. The aversion was obtained in both forced- and free-choice tests. A 2–4 fold differential in efficacy was found when the same dose levels of both amphetamine isomers were tested for their effects in reducing water intake. The approximately 4-fold greater effectiveness of the d-isomer suggested that the taste aversion may be mediated by a dopaminergic system. In addition, it was suggested that the taste aversion behavior represented a conditioned anorexic effect rather than being indicative of a noxious or aversive consequence of the amphetamine.
TL;DR: In the schedule-induced group, severe tonic-clonic seizures occured as a result of ethanol withdrawal, and the home-cage animals showed no sign of an abstinence syndrome upon substitution of water for ethanol.
Abstract: The effect of adding sodium saccharin to a 5% ethanol solution on intake was examined. One set of animals were maintained at 80% of their free-feeding weight, in their home-cages with either 5% ethanol, or 5% ethanol-0.25% sodium saccharin as the only fluid available for three months (home-cage condition). A second set of animals were maintained in cages with automatic food dispensers that provided a 24 hr feeding regimen known to produce ethanol overdrinking (schedule-induced condition). These animals had 5% ethanol as their only available fluid for one month, followed by the 5% ethanol-0.25% sodium saccharin mixture for two months. No significant differences in ethanol intake were found between the 2 home-cage conditions (5% ethanol = 11.6 g ethanol/kg/day; 5% ethanol in 0.25% sodium saccharin = 11.7 g ethanol/kg/day. However, the addition of saccharin in the schedule-induced condition produced a marked increase in ethanol intake (5% ethanol = 13.1 g ethanol/kg/day; 5% ethanol in 0.25% sodium saccharin = 15.1 g ethanol/kg/day). The home-cage animals showed no sign of an abstinence syndrome upon substitution of water for ethanol. In the schedule-induced group, severe tonic-clonic seizures occured as a result of ethanol withdrawal.
TL;DR: The results are discussed according to the previously expressed suggestion about the possible inhibitory role of serotonin in apomorphine-induced locomotor stimulation in rats.
Abstract: The locomotor activity of rats injected with apomorphine (1.0 or 5.0 mg/kg) was measured. The increase of locomotion caused by apomorphine was stronger in rats pretreated with BOL or methysergide and in some case with p-chloroamphetamine. LSD did not change the stimulation evoked by apomorphine or decreased it. The results are discussed according to the previously expressed suggestion about the possible inhibitory role of serotonin in apomorphine-induced locomotor stimulation in rats.
TL;DR: LSD appeared to augment sensitization rather than acting on the startle circuit directly since it did not increase startle unless given in conjunction with either background noise or repetitive tones.
Abstract: In 4 experiments the effect of d-lysergic acid diethylamide (LSD) on the acoustic startle response in rats was measured A low dose (20 μg/kg) facilitated startle but a high dose (160 μg/kg) at first facilitated but then depressed startle somewhat relative to an intermediate dose (40 μg/kg) 2-brom LSD (199 μg/kg) had no detectable effect and 40 μg/kg LSD did not change startle in raphe-lesioned rats LSD appeared to augment sensitization rather than acting on the startle circuit directly since it did not increase startle unless given in conjunction with either background noise or repetitive tones LSD did not prevent between session habituation Relationships between habituation, sensitization, and the midbrain raphe nuclei were discussed
TL;DR: No rage reaction can be evoked by carbachol stimulation of the globus pallidus, putamen, dorsal hippocampus, ventral hippocampus, anterior, basal, central or lateral amygdaloid nucleus and the cerebral white matter.
Abstract: The rage reaction which can be evoked by carbachol stimulation of the hypothalamus on freely moving cat is not specific for the hypothalamus by far. It can also be elicited by carbachol stimulation of the septal region, thalamus (intralaminary nuclei), central grey matter, red nucleus, mesencephalic reticular formation as well as by injecting the drug into the cerebral ventricle. No rage reaction can be evoked by carbachol stimulation of the globus pallidus, putamen, dorsal hippocampus, ventral hippocampus, anterior, basal, central or lateral amygdaloid nucleus and the cerebral white matter. The significance of these findings is discussed.
TL;DR: The results suggest that the suppression of alcohol drinking is not dependent upon those factors, such as the ability to show an alcohol-deprivation effect, which develop during prolonged access to alcohol.
Abstract: Two groups of 14 male Sprague-Dawley rats were given either 1 or 32 days of voluntary access respectively to 7% (v/v) ethanol solution before being injected once with 30 mg/kg of morphine. Alcohol consumption during the subsequent week was suppressed to about the same extent in both cases. Food intake was slightly reduced and water drinking increased in both groups after the morphine injection. The only difference observed between the effects after 1 and 32 days of alcohol access was that in the latter there was a significant negative correlation (r = −.891) between the reductions in alcohol and food consumption. The results suggest that the suppression of alcohol drinking is not dependent upon those factors, such as the ability to show an alcohol-deprivation effect, which develop during prolonged access to alcohol.