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Effects of low and moderate doses of chlorpromazine on discrimination learning in the rat.

The effects of chlorpromazine on the acquisition of a brightness discrimination with food reward were examined. Doses of 0.5, 1.0 or 2.0 mg/kg of CPZ as well as saline were administered intraperitoneally to 4 groups of 7 Sprague-Dawley rats, 1 h prior to testing. After a 3-week period of habituation and pre-training, rats were tested 20 trials a day, 7 days a week. No drug effect was found on the number of trials to reach a criterion of 18/20 successive correct responses, which required an average of 6.2 days of training. Precriterion latencies, however, showed an increase as a function of increasing dose level. Post-choice latencies were not affected, eliminating motor retardation as an explanation for the latency effect.

Animals↗

Repeated testing within drug discrimination learning: time course studies with cocaine, amphetamine, and 3-PPP.

Pigeons were trained to discriminate between 3 mg/kg cocaine and saline. Tests with cocaine and amphetamine were conducted at different intervals after administration to compare the time course of the discriminative stimulus (DS) effects. Tests were of two kinds: a) separate, that is, only one dose and interval were examined on each separate test day; and b) repeated, that is, all three intervals were assessed after a single administration of the drug dose during 1 test day. Separate and repeated determinations of the time course yielded similar estimates. The duration of the DS effects of amphetamine were longer than those of cocaine. No apparent difference, either with regard to duration of effect or potency, existed between (+)- and (-)-amphetamine. The potency of cocaine was similar to that of the amphetamine isomers. The dopamine autoreceptor blockers (+)- and (-)-3-(hydroxyphenyl)-N-n-propylpiperidine (3-PPP) (1-10 mg/kg) engendered less than 44% cocaine-associated responding for the repeatedly examined intervals (15, 60, and 120 min after administration). The results of this study encourage the use of repeated testing methodology to assess the duration of action of the DS effects of drugs.

Amphetamine↗

Corpus callosum section disrupts motor behaviour strategies during visual discrimination learning in rat.

Monocularly patched rats were trained on a series of visual tilt discriminations ordered from simple to difficult to measure the angular difference threshold of each eye. The stereotyped running pattern which the animal made was also recorded. Callosal section disrupted a preoperatively established running pattern and produced an ocular neglect; the animal's performance dropped to chance when it used the eye ipsilateral to the preferred side of approach.

Animals↗