Methamphetamine‐induced conditioned place preference in male rats eating standard or high fat chow

Abstract

Eating a high fat diet has several negative health consequences, including dysfunction to dopamine systems. It has also been shown to enhance the sensitivity of male rats to methamphetamine-induced locomotor sensitization. However, it is not known if sensitivity to the other (i.e., rewarding) effects of methamphetamine are similarly enhanced in rats eating a high fat diet. To test the hypothesis that eating high fat chow enhances sensitivity of rats to the rewarding effects of methamphetamine, male Sprague Dawley rats were fed standard (17% kcal from fat) or high fat chow (60% kcal from fat) for 4 weeks prior to conditioned place preference (CPP) training, using a biased design. Before training, rats were given free access to both sides of the chamber to determine a side preference. Rats were then trained on alternating days with saline or methamphetamine (0.1, 0.32 and 1.0 mg/kg, i.p.) with drug conditioned in the initially non-preferred side. A 2 × 4 between-subjects ANOVA revealed a significant main effect of methamphetamine dose, but no main effect of diet, and no significant diet × dose interaction effect. Tukey HSD post-hoc analyses revealed that male rats conditioned with 0.32 mg/kg and 1.0 mg/kg methamphetamine displayed significantly larger preference scores than male rats conditioned with saline, regardless of diet. That is, at the two largest doses, methamphetamine induced a significant CPP. Preference scores for rats conditioned with the smallest dose of methamphetamine (0.1 mg/kg) did not significantly differ from the saline conditioned group nor the two larger doses of methamphetamine. Though no effect of diet was found, in contrast to what might have been predicted based on previous studies with methamphetamine-induced locomotion, future studies should explore a wider range of doses, as well as other assays (e.g., intravenous self-administration). Future studies will also examine female rats to investigate potential sex differences.