GATING OF AUDITORY P50 IN SCHIZOPHRENICS - UNIQUE EFFECTS OF CLOZAPINE

Schizophrenic patients have a deficit in the ability to filter sensory stimuli, which can be demonstrated in several psychophysiological par adigms. For example, most unmedicated schizophrenic subjects fail to d ecrement the P50 auditory evoked response to the second of paired stim uli, when the interstimulus interval is 500 msec, This sensory gating deficit persists in schizophrenics treated with typical antipsychotics , even if they show significant clinical improvement, When the interst imulus interval is 100 msec, most schizophrenics exhibit impaired gati ng while acutely ill, but normalize with treatment Clozapine, the prot otypic atypical antipsychotic medication, is clinically more effective than conventional neuroleptics in a significant proportion of schizop hrenics refractory to other drug treatment, Nine schizophrenic subject s who were refractory to conventional neuroleptic treatment were studi ed while being treated with typical neuroleptics and then restudied af ter I month's treatment with clozapine. In the six clozapine responder s, there was significant improvement of P50 gating at the 500 msec int erval. At the 100 msec interval there was an inverse relationship betw een sensory gating of P50 and clozapine dose, independent of clinical response. Thus, although this can only be considered preliminary data because of the small numbers of subjects, it appears that clozapine, c ompared to typical neuroleptics, has distinct effects on P50 gating.