Differences in the effects of post-trial chlorpromazine, reserpine, and amphetamine on discrimination learning in rats

Abstract

Rats were trained to perform in discrimination learning reinforced by water for 6 days, and were intraperitoneally injected with chlorpromazine, reserpine, or d-amphetamine after each training session. Although chlorpromazine at the dose levels of 0.5 mg/kg or more injected immediately after training impaired learning, the drug did not affect learning when it was injected 60 min after training. Reserpine and amphetamine also impaired learning, but delaying the time intervals between training and injection to 60 min or more had no influence on this learning impairment. Post-trial chlorpromazine and amphetamine had no effect on, but reserpine decreased, motility in the subsequent training session. Chlorpromazine had no effect on water intake in the subsequent session, but reserpine and amphetamine decreased water intake at the dose levels that impaired learning. It was concluded that all three drugs impaired learning, but differed in their effects on learning; chlorpromazine impaired learning by a specific effect on learning itself; reserpine, by a non-specific effect on behavior due to a long acting sedation; and amphetamine, by an effect to decrease the motivation to drink water. The specific effect of chlorpromazine could be related to the hypothesis of "memory trace" synthesis.

Effects of amphetamine on the plus-maze discriminative avoidance task in mice

“…This effect has been shown in several animal models, including the conventional elevated plusmaze, where the administration of 4.0 mg/kg amphetamine increased the total number of entries in open or enclosed arms (Lister 1987). The motor stimulating effect could interfere with the acquisition of different behavioral tasks and consequently affect retention in pretraining amphetamine-treated animals, and this issue has been discussed in some studies, most of them excluding this possibility (Roffman and Lal 1971;Ishikawa and Saito 1976;Roozendaal et al 1996). In the present study, however, this well-known effect of amphetamine was not verified, since there was no change in the total number of entries due to amphetamine treatment in the experiment-I training session.…”

Divergent Effects of Haloperidol on Motor Versus Spatial Functions

“…Yet the infl uence of the limbic system is further indicated by poorer discrimination learning after post-trial intrahippocampal injection of haloperidol in rats [63]. Moreover, post-trial IP injections of CPZ slowed down acquisition of a discrimination task in water-deprived rats [64]. Pre-trial neuroleptic administration can also impair limbicdependent recognition memory, as shown by deteriorated matching-to-sample performance between seven geometric symbols in monkeys [65], and two color-matching in pigeons [66,67], though not two color-matching [42], or clip art and digitized photo non-matching [62], in monkeys.…”