Individual differences in sugar consumption following systemic or intraaccumbens administration of low doses of amphetamine in nondeprived rats

Rats exhibit individual differences in their propensity to ingest sucrose and in their feeding response to low doses of amphetamine (AMP). Rats with high baseline sugar intake (HIGH) show a decrease in sugar consumption in response to AMP, while rats with low baseline sugar intake (LOW) show an increase in consumption (33,34). At present, it is not known whether LOW and HIGH rats would be differentially responsive to higher, anorexigenic doses of AMP. Thus. the present study was developed to further determine the dose-response curve for AMP's effects on sugar consumption in LOW and HIGH rats. One group of rats received IP injections of 0.05, 0.1, and 0.2 mg/kg AMP, while a second group was administered 0.25, 0.5, and 1.0 mg/kg AMP. A third group of rats received intranucleus accumbens (Acc) microinjections of low to moderate (2.0-8.0 mu g) doses of AMP, because evidence indicates that this may be an important site of action for AMP's effects on feeding in LOW and HIGH rats. Results showed that at low doses (less than or equal to 0.25 mg/kg), AMP stimulated sugar consumption in LOW rats and either had no effect or inhibited consumption in HIGH rats. At doses greater than 0.25 mg/kg, AMP inhibited sugar consumption in both LOW and HIGH rats. Furthermore, intra-Acc administration of AMP stimulated sugar intake in LOW rats and produced a slight, but nonsignificant, decrease in consumption in HIGH rats. Taken together, these results show that LOW and HIGH rats exhibit individual differences in their feeding response to low but not moderate to high doses of AMP. Furthermore, the evidence indicates that the Ace is an important site for AMP's facilitatory effect on sugar consumption in LOW rats.