Cocaine-induced sniffing stereotypy changes in response to threat.

"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.

Cocaine produces panic-like flight responses in mice in the mouse defense test battery.

There is an emerging body of clinical evidence that cocaine use in humans can result in serious fear or panic-related emotional disturbances. The present study evaluated the effects of cocaine administration upon defensive responses of mice to a predator (rat) in a Mouse Defense Test Battery (MDTB) that permits the display of the full range of the mouse defensive behaviors: avoidance/escape, flight, freezing, defensive upright, and defensive threat and attack. Mice were tested 30 min following intraperitoneal (IP) injections of either 0, 10, 20, or 30 mg/kg cocaine hydrochloride suspended in physiological saline. Cocaine produced an increase in flight and escape responses throughout the subtests comprising the MDTB. The percentage of subjects exhibiting escape increased in cocaine-treated mice in the Predator Avoidance Test. Cocaine increased mean flight speed and maximum flight speed in the Flight/Chase Test; frequency of flight responses in the Straight Alley Test; and the number of flight attempts in the Forced Contact test. The predominance of flight responding throughout the tests masked any possible cocaine effects on other defenses. The present findings indicate that cocaine may exert its panic-producing effects by acting upon particular neurobehavioral systems subserving defensive behavior.