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J C Winter

Publications and source records attributed to J C Winter.

At least 91 records · Page 5Linked to original sources
PubMed1978

Yohimbine-induced stimulus control in the rat.

Rats were first trained in a 2-lever operant test chamber using a fixed ratio 10 schedule of water reinforcement. Discrimination training was then begun. In sessions following the injection (i.p.) of yohimbine . HC1 (3 mg/kg), responses on 1 of the 2 levers were reinforced. In sessions following the injection of saline, responses on the remaining lever were reinforced. The distribution of responses between the 2 levers prior to reinforcement provided an index of discrimination. The criterion for stimulus control was set at 80% correct responses in each of five consecutive sessions. In a group of six rats, criterion performance was begun after a mean of 33 sessions. Cross tests were conducted in yohimbine-trained subjects with d-amphetamine, harmaline, and LSD. Each test drug yielded intermediate results, i.e., response distribution was significantly different from both the yohimbine and the saline training conditions. No significant antagonism of yohimbine-induced stimulus control was achieved with BC-105, phentolamine, or butaclamol, purported antagonists at serotonergic, alpha-adrenergic, and dopaminergic receptor sites, respectively.

Animals↗
PubMed1977

Morphine and ethanol as discriminative stimuli: absence of antagonism by p-chlorophenylalanine methyl ester, cinanserin, or BC-105.

It is well established that the effects of morphine and ethanol can function as discriminative stimuli in the rat. The present investigation sought to determine whether discriminated responding mediated by morphine and ethanol is affected by (a) p-chlorophenylalanine methyl ester (p-CPA) an inhibitor of the synthesis of 5-hydroxytryptamine (5-HT) and (b) antagonists of 5-HT. The blocking agents employed were cinanserin, in ethanol-trained subjects, and BC-105, in morphine-trained subjects. No evidence of antagonism was obtained with either BC-105 or cinanserin. Results with p-CPA were somewhat variable but no consistent or statistically significant reduction in the efficacy of morphine or ethanol as discriminative stimuli was observed. The present results with p-CPA are at variance with earlier work by Schechter (1973) and by Rosecrans et al. (1973) who observed antagonism of the stimulus effects of ethanol and morphine, respectively, following depletion of 5-HT with p-chlorophenylalanine.

Animals↗
PubMed1975

The stimulus properties of morphine and ethanol.

The present investigation sought (a) to establish the efficacy of morphine and ethanol as discriminative stimuli when each is paired with the administration of saline and (b) to compare, in a qualitative sense, the stimulus properties of the two drugs. Additional experiments examined the effects of treatment with naloxone or l-propranolol upon morphine and ethanol-mediated discriminated responding. Finally, the stereospecificity of the stimuli produced by morphine was determined by a comparison, in morphine-trained rats, of levorphanol and dextrorphan. Discriminated responding developed rapidly in both the morphine and ethanol groups. In tests in which ethanol was administered to morphine-trained animals and vice versa, no similarity to stimulus properties was apparent. Antagonism of discriminated responding induced by morphine and ethanol was attempted using naloxone and l-propranolol. Naloxone blocked the actions of morphine but was without effect upon ethanol. No evidence of antagonism of either drug by propranolol was found. When a range of doses of levorphanol (0.1-3 mg/kg) and dextrorphan (3-100 mg/kg) was tested in morphine trained animals, only levorphanol was able to substitute for morphine. The present results suggest that the stimulus properties of morphine represent typical opiate effects.

Animals↗
PubMed1975

The effects of 2,5-dimethoxy-4-methylamphetamine (DOM), 2,5-dimethoxy-4-ethylamphetamine (DOET), d-amphetamine, and cocaine in rats trained with mescaline as a discriminative stimulus.

The effects of mescaline (3,4,5-trimethoxyphenylethylamine), a hallucinogen, can function as a discriminative stimulus in appropriately trained rats. As a test of the hypothesis that those pharmacologic properties which distinguish hallucinogens and non-hallucinogens in man are reflected in distinctive stimuli in rats, the present experiments examined the effects of 2,5-dimethoxy-4-methylamphetamine (DOM), 2,5-dimethoxy-4-ethylamphetamine (DOET), d-amphetamine, and cocaine in rats trained with mescaline as a discriminative stimulus. Administration of a range of doses of DOM and DOET to subjects in which saline functioned as SD and mescaline as Sdelta revealed that a dose of 0.3 mg of either DOM or DOET was equivalent to the training dose of mescaline. When tested in rats in which mescaline served as SD, DOM and DOET were likewise found to mimic mescaline. In contrast, doses of d-amphetamine and cocaine (1 and 30 mg/kg, respectively) which were equivalent to the training dose of mescaline as Sdelta, did not result in responding appropriate for the mescaline condition when mescaline was trained as SD. When DOET (0.3 mg/kg) was substituted for saline as Sdelta, no evidence of discriminated responding was obtained in the course of 50 sessions. The present data, in conjunction with previous observations, suggest that those effects of mescaline in the rat which function as a discriminative stimulus are better correlated with pre-hallucinogenic LSD-like activity in man then with hallucinogenic activity per se. Thus, these effects in rats represent a necessary but not a sufficient condition for prediction of hallucinogenic activity in man.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1975

Assessment of tolerance to barbital by means of drug discrimination procedures.

This study was designed to determine the relative development of tolerance to the discriminative-stimulus and hypnotic properties of barbital. By selectively reinforcing lever presses only in the presence of one of the drug stated, rats were trained in a Skinner Box to discriminate the effect of sodium barbital (80 mg/kg) injection from that of saline injection. After the rats were well trained, the administration of daily hypnotic doses of barbital (240 mg/kg) for 8 days produced marked tolerance to the hypnotic effect of the barviturate in all animals. The ability of the 80 mg/kg dose to serve as a discriminative stimulus was not impaired in animals which had been trained with the drug as the condition during which bar presses had been reinforced (SD condition). Animals for which bar presses had gone unrewarded under barbital (Sdelta condition) displayed a tendency to develop tolerance to the stimulus properties of barbital. These findings are interpreted in the light of dose-effect studies, and it is suggested that the acquired polarity of the drug condition determined by its assignment as Sd or Sdelta may influence the discriminability of the drug in future exposures.

Animals↗
PubMed1975

Long-term effects of barbital on spontaneous activity of rats trained to use the drug as a discriminative stimulus.

This investigation sought to determine if the discriminative stimulus properties of barbital are reflected in the pattern of spontaneous motor activity induced by the drug. Rats were trained in a Skinner box to discriminate the effects of sodium barbital (80 mg/kg), injected 60 min prior to training, from those of saline. Half of the animals (Group I) were taught the drug discrimination by rewarding them for bar pressing only when they were in the drug condition. The other half of the animals (Group II) were rewarded only in the absence of the effects of barbital. Spontaneous motor activity was monitored during the 20 min period from 40--60 min after injection of the drug or saline. After several months of drug discrimination training, the patterns of spontaneous activity displayed by all animals suggested that the treatments had become conditioned to signal the forthcoming availability or non-availability of food in the Skinner box. The data also suggested that chronic exposure to barbital may induced adaptations which allowed the drug to increase spontaneous motor activity.

Animals↗
PubMed1975

Blockade of the stimulus properties of mescaline by a serotonin antagonist.

It is known that the effects of mescaline (3, 4, 5-trimethoxyphenylethylamine), a hallucinogen, can function as a discriminative stimulus. The present investigation examined the ability of cinanserin, a serotinin antagonist, to block the stimulus properties of mescaline in the rat. After a reliable discrimination was established between the effects following the injection of mescaline (10 mg/kg) and those following administration of saline, subjects were pretreated with cinanserin HC1 (3 mg/kg) and then treated with mescaline. Such pretreatment was found to block discrimination, i.e., the response rate following the administration of mescaline plus cinanserin was appropriate for the saline condition. The present data suggest that antagonists of serotonin may be useful in furthering our understanding of phenethylamine hallucinogens.

Animals↗