COCAINE PREEXPOSURE SENSITIZES CONDITIONED FEAR IN A POTENTIATED ACOUSTIC STARTLE PARADIGM

The consequences of chronic cocaine administration on fear-potentiated startle were evaluated in two experiments. Cocaine treatment (40 mg/k g) for 7 days prior to fear acquisition (light + shock pairings) had a n attenuating influence on the ability of the conditioned stimulus (CS ) to increase acoustic startle. When cocaine was administered in the c ontext of the CS, following fear conditioning, a marked enhancement of potentiated startle was observed. In contrast, an extinction of the f ear response was seen in saline and procaine animals repeatedly expose d to the nonreinforced CS. The results from control subjects injected with cocaine either in the shock chambers (contextual cues) or in thei r home cage environment, suggest that the systemic effects of this sti mulant served to intensify the fear-eliciting properties acquired by t he CS during fear conditioning. These findings demonstrate a cocaine s ensitization of conditioned fear, and were related to the emotional an d psychological disturbances associated with long-term cocaine use.