Cocaine-induced sniffing stereotypy changes in response to threat

Cocaine induced stereotypies" have been extensively investigated on the bas is that they may be capable of providing insights into behavioral and neuro chemical mechanisms relevant to drug abuse and addiction. Recent work has i ndicated that cocaine enhances a number of defensive behaviors, and, that c ocaine-enhanced sniffing may be a functional behavior pattern, potentially related to defense, prompting an investigation of the effects of threat sti muli on cocaine-enhanced sniffing. When behaviors of saline control rats we re evaluated in their home cages (HC), or on exposure to a toy cat (TC) or real cat (RC)? they showed minimal crouching in the HC; initial crouching d eclining over 5 days of repetitions to the TC; and continued, high-level cr ouching to the RC. Cocaine (30 mg/kg, IF) enhanced defensiveness in situati ons in which it had declined in the TC and RC groups. It also produced high -level sniffing, declining over 5 test days, in the HC; initial low-level s niffing to the TC, increasing over 5 test days. and very low levels of snif fing to the RC. These and previous data contribute to a view that cocaine e nhances, but does not directly induce, defensive behaviors. They also indic ate that external threat stimuli such as the RC, or initial presentation of the TC suppress sniffing, with sniffing returning as habituation to novel but not intrinsically dangerous stimuli reduces defensiveness. This view su ggests that some component of "sensitization of cocaine-induced sniffing st ereotypy" may reflect a release from defensiveness-mediated suppression of sniffing over repeated injection/testing as the subject becomes habituated to the injection procedure and to novel test situations. (C) 2000 Elsevier Science Inc.