Chronic intake of a cafeteria diet and subsequent abstinence. Sex-specific effects on gene expression in the mesolimbic reward system

Studies examining the impact of chronic palatable food intake on the mesolimbic reward system have been conducted almost exclusively in males. This study aimed to determine the effects of chronic intake of a palatable cafeteria diet and subsequent abstinence on fat mass, food intake and key gene expression of the mesolimbic reward system in both males and females. Albino Wistar rats were fed for 8 weeks on standard chow (Control, n = 5 males, 5 females) or cafeteria diet (CD; n = 16 males, 16 females). The cafeteria diet was then removed from a subset of CD rats for 72 h (CD-Withdrawal group, CD-W). The nucleus accumbens (NAc) was isolated and mRNA expression of tyrosine hydroxylase (TH), dopamine active transporter (DAT), D1 and D2 dopamine receptors, and μ-opioid receptor determined by qRT-PCR. Chronic cafeteria diet intake increased fat mass in all CD rats but body weight and chow intake were reduced during the period of cafeteria diet abstinence. TH mRNA was reduced in male CD and CD-W rats, but increased in female CD and CD-W rats. D1 mRNA was reduced in CD and CD-W females, but increased in CD males, compared to Controls. μ-opioid receptor expression was reduced in CD and CD-W males but not females. These data highlight the importance of investigating sex differences in the neurobiological response to palatable food intake and the need for future studies in this area to include both sexes.