Effects of haloperidol and clozapine on sensorimotor gating deficits induced by 5-hydroxytryptamine depletion in the brain.

Evidence is increasing for a role of brain 5-hydroxytryptamine (5-HT) systems in schizophrenia. We previously showed that brain 5-HT depletion causes disruption of prepulse inhibition, a measure of sensorimotor gating that is deficient in schizophrenia. Antipsychotic treatment has been reported to reverse these deficits in patients with schizophrenia. The present study was designed to investigate the ability of antipsychotic drugs to reverse prepulse inhibition deficits caused by lesions of the brain 5-HT system in rats. In male Sprague-Dawley rats, selected parts of the brain 5-HT systems were lesioned by micro-injection of the 5-HT neurotoxin 5,7-dihydroxytryptamine into the dorsal raphe nucleus (DRN) or median raphe nucleus (MRN). The effects of antipsychotic drugs on lesion-induced changes in prepulse inhibition were examined 2 weeks after the surgery. There was significant disruption of prepulse inhibition in the MRN-lesioned group compared to sham-operated controls. This deficiency in prepulse inhibition was restored by clozapine (1 and 5 mg kg(-1)) treatment, and by treatment with a relatively high dose of haloperidol (0.25 mg kg(-1)). There was no significant effect of the DRN lesions on prepulse inhibition compared with sham-operated controls. These results indicate that 5-HT depletion in MRN-innervated brain structures leads to disruption of prepulse inhibition. Treatment with both antipsychotic drugs, haloperidol and clozapine, significantly increased prepulse inhibition in these animals back to the level seen in sham-operated controls. The present findings highlight the importance of the 5-HT systems in cognitive models of schizophrenia.