Individual differences in behavior following amphetamine, GBR-12909, or apomorphine but not SKF-38393 or quinpirole

Subjects that respond more to a novel environment show a greater locomotor response to drugs of abuse such as cocaine and amphetamine. The current study was performed to examine differences between high (HR) and low (LR) responding rats to a novel environment following administration of amphetamine, a selective dopamine uptake blocker (GBR-12909), a nonselective dopamine agonist (apomorphine), and selective dopamine D1 and D2/D3 agonists. A behavioral checklist and a rating scale were used to determine the behavioral arousal caused by administration of amphetamine (0, 0.5, 2.0, and 8.0 mg/kg), GBR-12909 (0, 1.25, 5.0, and 20.0 mg/kg), apomorphine (0, 0.1, 0.3, and 1 mg/kg), SKF 39393 (0, 2.5, 10, and 40 mg/kg), or quinpirole (0, 0.05, 0.5, and 5.0 mg/kg). The five drugs produced behavioral activation profiles distinct from each other. Following amphetamine administration, both HR and LR subjects showed dose dependent increases in behavioral arousal. The behaviors primarily affected were sniffing, locomotor activity, rearing, and oral activity. HR rats showed a greater overall behavioral response to amphetamine administration compared with LR rats and there were differences in specific behaviors between the two groups. Following GBR-12909 administration, all subjects showed dose dependent increases in sniffing, locomotor activity, and rearing. Differences between HR and LR were observed in sniffing, locomotor activity, and rearing behaviors. HR and LR both showed dose dependent increases in behavior following apomorphine administration. HR showed greater behavioral activation after apomorphine than LR.(ABSTRACT TRUNCATED AT 250 WORDS)