PubMed2000
"Cocaine-induced stereotypies" have been extensively investigated on the basis that they may be capable of providing insights into behavioral and neurochemical mechanisms relevant to drug abuse and addiction. Recent work has indicated that cocaine enhances a number of defensive behaviors, and, that cocaine-enhanced sniffing may be a functional behavior pattern, potentially related to defense, prompting an investigation of the effects of threat stimuli on cocaine-enhanced sniffing. When behaviors of saline control rats were 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 declining over 5 days of repetitions to the TC; and continued, high-level crouching to the RC. Cocaine (30 mg/kg, IP) enhanced defensiveness in situations 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 sniffing to the TC, increasing over 5 test days; and very low levels of sniffing to the RC. These and previous data contribute to a view that cocaine enhances, but does not directly induce, defensive behaviors. They also indicate 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 suggests that some component of "sensitization of cocaine-induced sniffing stereotypy" 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.