Increased startle responding in rats treated with phencyclidine.

Male rats were given subcutaneous injections of saline or 0.25 to 5.0 mg/kg phencyclidine (PCP) either five or 35 minutes prior to being presented with 121 startling tactile (air-puff) stimuli at 15 second intervals. Phencyclidine increased startle with an inverted-U dose-response relationship, the maximal increase being produced by 1.0 mg/kg. Doses of 0.5 or 1.0 mg/kg PCP also produced a reduced rate of behavioral habituation, which, in the latter case, was shown to be independent of the time since drug administration. These results are interpreted as indicative of an impairment of behavioral habituation being the threshold effect of PCP on tactile startle.