YOHIMBINE IMPAIRS P50 AUDITORY SENSORY GATING IN NORMAL SUBJECTS

The evoked response to repeated auditory stimuli generally decreases i n amplitude, a phenomenon that demonstrates the activity of sensory ga ting mechanisms in the central nervous system (CNS). Gating of the P50 wave of the auditory evoked response shows such behavior in normals, but not in schizophrenic or manic subjects. In mania, diminished gatin g of the auditory evoked response is correlated with elevated levels o f noradrenergic metabolites. In animals, yohimbine, a presynaptic alph a-2 antagonist, increases noradrenergic neuronal transmission in the C NS and diminished gating of the auditory evoked response. The aim of t his experiment was to test whether yohimbine causes diminished auditor y sensory gating in normal human controls. Seven normal subjects with normal P50 auditory gating were treated either with 0.4 mg/kg of oral yohimbine on one day or placebo on a different day. Each subject acted as his own control. Yohimbine, but not placebo, caused a significant but transient decrease in P50 auditory gating in these subjects. Thus, increasing CNS noradrenergic neuronal transmission in normal controls can cause a transient impairment in auditory sensory gating.