Sensory gating deficit following cocaine exposure in the rat.

The purpose of this research was to examine changes in the ratio and amplitude of the N40 component of the auditory event-related potential (ERP) in the paired conditioning (C) test (T) stimulation paradigm following subchronic cocaine/vehicle administration. Free moving rats received cocaine (47.5 mg/kg) or saline for 7 consecutive days in a longitudinal crossover design. ERPs were recorded 4 and 7 days after each treatment and again 4 and 7 days following withdrawal of the drug/vehicle. Cocaine led to a progressive increase in the T/C ratio indicating impaired inhibition of the test response. This trend continued throughout the 7-day drug regimen. Following withdrawal of the drug the T/C ratio gradually normalized over the next 7 days but remained elevated at 4 days postdrug. A significant increase in the test response accompanied by a less pronounced decrease in the conditioning response accounted for the observed results. Behavioral state as measured on a rating scale during ERP sampling did not differ across experimental conditions.