The effects of chlorpromazine on the decay and consolidation of short-term memory traces in mice

Chlorpromazine-induced psychosis after brain injury

Antipsychotic agents, most often used for treatment of schizophrenia, are sometimes prescribed for the agitated patient with an organic brain disorder. We report the case of a brain-injured patient who was prescribed chlorpromazine for agitation and who developed a delusional state while taking this antipsychotic agent. The emergence of this delusional state coincided with the exacerbation of certain cognitive deficits. Possible mechanisms for this phenomenon are discussed. Caution is advised when prescribing neuroleptics for patients with traumatic brain injury, especially those agents with significant cognitive side-effects or with a significant potential to precipitate seizures.

Baclofen disrupts passive avoidance retention in rats

Baclofen (Lioresal, Ciba-Geigy) is an analog of the inhibitory neurotransmitter GABA and is used clinically to control spasticity. Recent studies have demonstrated that this compound produces a marked inhibition of synaptically evoked responses in area CA3 of the hippocampal slice, suggesting that this drug could influence behavior mediated by the limbic system. In the present study, male rats of the Fischer-344 strain were trained on a one-trial passive avoidance task and tested for retention 1 week later. After the training trial, separate groups of rats received either 5 or 10 mg/kg/4 ml IP of baclofen or the distilled H2O vehicle immediately, 10 min, or 60 min after training. One week later, the rats that received baclofen immediately after training reentered the test chamber with a significantly higher frequency than controls, although no differences in vacillatory responses were observed between groups. Similar effects were observed following posttrial administration of chlordiazepoxide. In a separate experiment rats were tested for locomotor activity after receiving the same doses of baclofen. Although baclofen decreased activity during a 30-min period after dosing, rats exposed to baclofen showed no significant change in activity relative to controls 1 week later. These data are consistent with the interpretation that baclofen may interfere with memory consolidation or retention.

The relationship between stereotypy and memory improvement produced by amphetamine

This study examined the possibility that amphetamine-induced stereotypy and facilitation of memory consolidation are both mediated by amphetamine's stimulation of dopaminergic activity in the caudate nucleus. In the first experiment, rats were given pairings of a tone and a shock followed by SC amphetamine (2 mg/kg). The amount of stereotypy and increased locomotor activity produced by the injection were measured immediately. Retention of the tone-shock association was evaluated 48 h later by observing the ability of the tone to suppress drinking. The degree of retention was significantly correlated with the amount of stereotypy but not with the amount of locomotion previously measured. In the second experiment, amphetamine was microinjected into the caudate nucleus (10 micrograms/microliters) and its ability to produce the same three behavioral effects was examined. These injections produced increased stereotypy and improved retention, but no increase in locomotion. The correlation of memory facilitation with stereotypy and the fact that both were produced by intracaudate amphetamine suggest that they may be mediated by the same neuropharmacological substrate, namely amphetamine-induced release of dopamine in the caudate.

Psychoactive drugs and stimulus analysis: III. Adjustment of behavioural measures for drug-induced memory effects and state dependence: the case of chlorpromazine

Chlorpromazine is shown to have a suppressant effect upon stimulus analysis when given intraperitoneally as a 1 mg/kg dose to rats. The drug has no effects upon motor activity at this dose, but does impair short-term memory. These findings are based upon an examination of chlorpromazine in a newly-designed psychoactive drug classification test which allows adjustments to be made for drug-induced memory effects and for the influence of state dependence. The rationale for these adjustments to behavioural measures is presented in detail.

The effects of chlorpromazine and lithium on appetitive discrimination learning in the rat

Rats learned one of two appetitive discrimination tasks varying in terms of cognitive difficulty. Contrary to previous reports showing an impairment in the acquisition of avoidance tasks under the effects of either chlorpromazine (CPZ) or lithium, the results of this experiment indicate that neither drug retards the acquisition of appetitive tasks. Instead, at the highest doses used (2 and 3 mg/kg), CPZ decreased the number of trials required for the difficult task. Rats administered CPZ had longer reaction times than rats administered placebo, and therefore might have achieved criterion earlier because they spent more time in front of and on the discriminanda. The contrary results reported with avoidance tests concerning the effects of CPZ are explained in terms of the anxiety-reducing properties of CPZ, which might reduce drive without impairing cognitive ability.

Amnesia for random shapes following unilateral and bilateral electronvulsive shock therapy

Three 16-point shapes were shown to 15 patients before undergoing either unilateral or bilateral electroconvulsive therapy. They were then tested for recognition following therapy. The same subjects were similarly tested for recognition memory with no intervening shock. Analysis of variance indicated no significant differential effects of the two methods of electroshock application.