EFFECTS OF REPEATED COCAINE ADMINISTRATION ON SENSORY INHIBITION IN RATS - PRELIMINARY DATA

We have recently reported that acute administration of cocaine to rats alters their sensory inhibitory capacity as tested in a paired click paradigm (S-1/S-2). Whether such acutely induced changes are persisten t, is not known. In order to shed some light on the degree of spontane ous reversibility of cocaine-induced decreased sensory inhibition, rat s were tested immediately after cocaine administration and 9 days afte r cessation of cocaine exposure. Six rats received cocaine HCl 20mg/kg intraperitoneally and six rats received normal saline for 5 consecuti ve days. The amplitudes of the S-1 responses were significantly decrea sed in the cocaine animals during the injection days only, but not 9 d ays later. Two measures of sensory inhibition were employed, S-2/S-1 x 100 amplitude ratio and S-1-S-2 amplitude difference. The ratio measu re indicated a significant decrease in inhibitory capacity in the coca ine group during the injection days, and remained significantly decrea sed 9 days after cessation of cocaine administration. The data suggest that repeated cocaine administration can induced persistent deficit i n the ability of the rat's brain to inhibit incoming irrelevant sensor y stimuli. (C) 1997 Society of Biological Psychiatry.