Diminished Acoustic Startle in Chronic Cocaine Users

Abstract

Chronic cocaine use has been shown to produce neurochemical alterations which persist after acute withdrawal. This study assessed the effects of cocaine use on the acoustic startle response and sensorimotor gating using prepulse inhibition (PPI) of startle. Nine male control subjects (mean age = 41.6) and 15 male cocaine users (mean age = 43.2) were tested, the latter after heavy cocaine use ranging from 4 to 27 years (mean age = 16.7). Cocaine users had been cocaine free for four days to six months (mean = 17 days) at testing. Cocaine users exhibited a 68% reduction in startle amplitudes (F = 7.4; df = 1,22; p < .01) compared to controls. There were trends towards increased PPI in cocaine users under certain conditions; however, there were no significant main effects. These results indicate that chronic cocaine use produces impairment of the startle response which persists after cessation of cocaine use. These findings may reflect changes in the dopaminergic system resulting from chronic cocaine use.