Sensitivity to chlorpromazine effects on brain function of schizophrenics and normals. A preliminary report

Effects of remoxipride on measures of psychological performance in healthy volunteers

The acute psychomotor effects after oral doses of 30, 60 and 120 mg remoxipride, a new selective D2 receptor blocker, and placebo were investigated in a double-blind crossover study in 11 healthy male volunteers. Two out of the first three subjects given 120 mg remoxipride experienced marked akathisia, and therefore no subsequent subjects were given this dose. There were no other clearly drug-related adverse effects reported below 120 mg, although restlessness was reported at 60 mg. Remoxipride was associated with increases in error scores on a continuous attention task and on auditory vigilance, and with a reduction in critical flicker frequency, suggesting a decrease in arousal level. There were no significant changes in psychomotor measures such as choice reaction time, decision making time, or body sway. Subjective assessments using visual analogue scales showed a slight dose-related increase in drowsiness, while the calm-excited scale showed a small change in the excited direction with 30 mg only. The peak effects were at 4-6 h after drug intake, which was later than expected from previous pharmacokinetic data. These results indicate that remoxipride may have a slight depressant effect in the dose-range used. The pattern of changes is consistent with current theories on the role of dopamine in attention and arousal, and with the effects of other neuroleptics. It differs, however, from tranquilisers such as the benzodiazepines, which show a more global pattern of effects.

Differential sensitivity to the effects of psychotropic drugs: psychotics vs normals; Asian vs Western populations

The effects and side-effects of psychotropic drugs are determined by many variables, and the host factor is one of the most important. A lower sensitivity of schizophrenics than normals to the sedative effect of chlorpromazine and a manic depressives to imipramine were demonstrated quantitatively by a higher percent time of waking EEG following medication. The mean therapeutic dose of chlorpromazine for the manic state was found to be much lower in Japanese than in Western populations in a controlled study comparing the antimanic efficacy of carbamazepine and chlorpromazine. A lower therapeutic dose in Asian populations has been reported also on other antipsychotic drugs, lithium, and tricyclic antidepressants. The lower therapeutic dose level was discussed from the standpoint of transcultural psychopharmacology.

d-Amphetamine and punished responding: the role of catecholamines and anorexia

Rats were trained to press a lever for food on a schedule in which components of variable interval reinforcement (V12') alternated with conflict components in which every response resulted in food delivery and footshock. Low doses of d-amphetamine selectively suppressed responding in the conflict component in a dose-dependent manner, whereas prefeeding suppressed responding in both components. Pretreatment with noradrenergic blocking agents (propranolol, phentolamine and phenoxybenzamine) did not diminish the suppressant effect of d-amphetamine, but this effect was reduced by pretreatment with alpha-methyl-para-tyrosine methylester and dopamine blockers (spiroperidol, haloperidol and clozapine) indicating that d-amphetamine was exerting its selective suppressant effect via the release of dopamine. It is suggested that the effects of low doses d-amphetamine on behaviour in conflict situations may provide a useful model for investigating the mode of action of neuroleptic drugs.