THE EFFECTS OF THE NEW ANTIPSYCHOTIC, SERTINDOLE, ON LATENT INHIBITION IN RATS

Latent inhibition (LI) is a measure of retarded conditioning to a previously presented non reinforced stimulus, that is impaired in schizophrenic patients and in rats treated with amphetamine. Neuroleptic drugs are known to produce two effects in this paradigm: to antagonize amphetamine-induced disruption of LI, and to facilitate the development of LI when administered on their own. The present experiments tested the effects on LI of the new neuroleptic, sertindole. The experiments used a conditioned emotional response procedure in rats licking for water, consisting of three stages: pre-exposure, in which the to-be-conditioned stimulus (a tone) was repeatedly presented without being followed by reinforcement; conditioning, in which the pre-exposed stimulus was paired with reinforcement (a foot shock); and test, in which LI was indexed by degree of suppression of licking during tone presentation. In Experiment 1 the effects of 0.31, 1.3 and 5.0 mg/kg sertindole were assessed following pre-exposure to 40 non-reinforced tones. Experiment 2 tested the effects of 5 mg/kg on LI following pre-exposure to 10 nonreinforced tones. Experiment 3 investigated antagonism of amphetamine-induced disruption of LI by 5.0 mg/kg sertindole. The results demonstrated that sertindole (5.0 mg/kg) possesses a neuroleptic-like profile in the LI model: it facilitates the development of LI and antagonizes amphetamine-induced disruption of LI.