Prepulse inhibition of the acoustic startle response in cocaine-withdrawn rats

Prepulse inhibition (PPI) of startle is a sensorimotor gating task in which a low-intensity acoustic stimulus presented prior to a high-intensity, sta rtle-eliciting stimulus can attenuate the acoustic startle response (ASR). Previous studies on startle reactivity in cocaine-withdrawn rats have found minimal changes; the present study extends this work to the gating of ASR. In Experiment 1, rats were injected daily with either saline or cocaine (3 0 mg/kg ip) for 2 weeks. ASR and PPI were measured prior to, and at 3- and 11-day withdrawal from, the chronic treatment. No effect of cocaine treatme nt was found on either measure. In Experiment 2, treatment was extended to 8 weeks, and an earlier withdrawal time point (1 day) was added. Rats treat ed with cocaine for 8 weeks exhibited lower startle reactivity during withd rawal compared with saline-treated controls. PPI did not differ between tre atment groups. Thus, extended chronic treatment with cocaine rendered signi ficant effects on startle responsivity. Further, this finding mirrors the b lunted ASR exhibited in chronic cocaine users [Neuropsychopharmacology 22 ( 2000) 89.]. (C) 2001 Elsevier Science Inc. All rights reserved.