Psychiatry Research 120 (2003) 1–12 0165-1781/03/$ - see front matter  2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/S0165-1781(03)00161-6 Prepulse inhibition of acoustic startle in subjects with schizophrenia treated with olanzapine or haloperidol Erica Duncan *, Sandor Szilagyi , Marion Schwartz , Alena Kunzova , Shobhit Negi , a,b, c c c c Toby Efferen , Eric Peselow , Subhajit Chakravorty , Myrsini Stephanides , c c,d c c James Harmon, Dragana Bugarski-Kirola , Stephen Gonzenbach , John Rotrosen a c c,d Emory University School of Medicine, Atlanta, GA, USA a Mental Health Servicey116A, Atlanta Veterans Affairs Medical Center, 1670 Clairmont Road, Decatur, GA 30033, USA b Department of Veterans Affairs New York Harbor Healthcare System, New York, NY, USA c New York University School of Medicine, New York, NY, USA d Received 25 July 2002; received in revised form 8 May 2003; accepted 12 June 2003 Abstract Studies of the acoustic startle response and of its inhibition by the presentation of a non-startling preliminary stimulus (prepulse inhibition, PPI) have revealed deficits in PPI in schizophrenic subjects compared to healthy controls. Animal studies indicate that atypical antipsychotics improve PPI deficits induced by NMDA antagonists more consistently than typical antipsychotics. The effect of medication status on PPI in schizophrenia is unresolved in the literature. In the current study the effects on PPI of the atypical antipsychotic olanzapine and the typical antipsychotic haloperidol were compared to the unmedicated state in subjects with schizophrenia. In a between-group design, 11 schizophrenic subjects on olanzapine, 16 subjects on haloperidol, and 14 subjects who were on no medication received acoustic startle testing with PPI determination. ANOVAs revealed no significant differences in startle to pulse alone stimuli, habituation of startle, or PPI between the olanzapine, haloperidol and unmedicated groups. These 41 subjects with schizophrenia were compared to a group of 21 historical healthy controls and found to have reduced PPI. These data do not indicate a preferential effect of olanzapine compared to haloperidol on sensorimotor gating in schizophrenia. The results are consistent with the hypothesis that PPI impairments are relatively stable across treatment conditions.  2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Sensorimotor gating; Prepulse inhibition; Antipsychotic; Olanzapine; Haloperidol 1. Introduction The acoustic startle response (ASR) is a reflex *Corresponding author. Mental Health Servicey116A, VAMC, 1670 Clairmont Rd., Decatur, GA 30033, USA. Tel.: q1-404-321-6111; fax: q1-404-417-2911. E-mail address: EduncanMD@aol.com (E. Duncan). contraction of the skeletal muscle that occurs in all mammals as a response to a sudden, intense acoustic stimulus. It is mediated by a simple pontine based neural circuit that has been well defined (Davis et al., 1982; Davis, 1997; Koch, 1999; Fendt et al., 2001). In humans, the eye- blink component of the startle response elicited by