Abstract

Previous research using an animal model of relapse has shown that acute food deprivation will increase drug seeking. Recent evidence from humans, however, suggests that chronic food restriction rather than acute deprivation is related to increases in drug taking and relapse, emphasizing the need to develop an animal model to elucidate the mechanisms mediating the effects of chronic food restriction on drug seeking. We studied the effects of chronic food restriction during a period of abstinence on heroin seeking in rats. Results demonstrated an augmentation of heroin seeking in chronically food restricted rats with a history of heroin self-administration. Re-feeding prior to the drug seeking test or decreasing the length of the food restriction period prevented the augmentation of drug seeking. A combination of chronic food restriction and a concurrent state of hunger appear to be necessary for the augmentation of heroin seeking induced by food restriction. Previously, it was demonstrated that chronically food restricted rats display alterations in the mesolimbic dopamine system, a critical component of the reward system. Consequently, we assessed extracellular levels of dopamine in the nucleus accumbens, one of the major targets for mesolimbic dopamine neurons, during the drug seeking test, following chronic food restriction in abstinent rats with a history of heroin self-administration. Preliminary data indicate significantly higher levels of dopamine throughout the drug seeking test in the food restricted rats. Our findings suggest that food restriction-induced changes in dopamine release in the nucleus accumbens are associated with the augmentation of drug seeking in food restricted abstinent rats.