Pharmacological Specificity of Conditioned Avoidance Response Inhibition in Rats: Inhibition by Neuroleptics and Correlation to Dopamine Receptor Blockade

Abstract

The inhibitory effect of 36 neuroleptic compounds on conditioned avoidance response (CAR) and unconditioned escape response (UER) has been studied in rats. All neuroleptics antagonized CAR in doses below those inhibiting UER and below those inducing catalepsy. Stereospecificity was shown in two cases. Significant correlation was found between CAR inhibitory and cataleptogenic potency. Also inhibition of amphetamine induced stereotypy, affinity to ³H-haloperidol binding sites in vitro and clinical potency was significantly correlated to CAR inhibition. CAR and UER inhibition induced by cis(Z)-flupentixol and haloperidol was attenuated by scopolamine, but was only weakly influenced by methysergide and prazosin. Among a wide range of other CNS active compounds tested, CAR was inhibited by α₁-adrenergic antagonists, benzodiazepines, a barbiturate, GABA agonists, morphine and a serotonin agonist, but in doses inducing other motor disturbances. It is concluded that CAR inhibition is a sensitive test for dopamine receptor antagonists. However, additional α-adrenergic activity found for some neuroleptics (e.g. clozapine, chlorprothixene) may contribute to the CAR inhibitory potency. Additional antimuscarinic activity of neuroleptics may moderately attenuate CAR inhibition whereas serotonin receptor blockade is of minor importance.