Dopaminergic regulation of quiet biting attack behavior in the cat

The present study provides evidence for the involvement of dopamine in the regulation of quiet biting attack behavior. Utilizing monopolar electrodes, quiet biting attack was elicited by electrical stimulation of lateral hypothalamus in five cats. After stable baseline response latency values were established, the nonselective dopamine agonist, apomorphine, was administered peripherally (IP, 1.0, 1.4 and 1.8 mg/kg), and its effects upon the attack response were identified. Apomorphine significantly facilitated the occurrence of quiet biting attack in a dose- and time-dependent manner. Conversely, quiet biting attack behavior was also suppressed in a dose- and time-dependent manner by the selective D2 antagonist, spiperone (0.2, 0.4 and 0.8 mg/kg), but not by the selective D1 antagonist, SCH 23390 (0.8 mg/kg). Moreover, pretreatment with spiperone (0.2 mg/kg) completely blocked the facilitatory effects of 1.4 mg/kg of apomorphine, while SCH 23390 (0.8 mg/kg) pretreatment failed to alter apomorphine-induced facilitation of the attack response. In addition, neither apomorphine nor spiperone altered response latencies for hypothalamically elicited circling behavior. The results suggest that dopamine plays a significant role in the regulation of quiet biting attack behavior.