Behavioral responding and nucleus accumbens cell firing are unaltered following periods of abstinence from sucrose.

A critical feature of cocaine addiction is the strong propensity to relapse following periods of abstinence. Here, we examined whether abstinence from sucrose self-administration in rats altered behavioral responding and nucleus accumbens (NAc) cell firing in a manner similar to that observed following cocaine abstinence. Rats (n = 22) were trained to self-administer sucrose on a short-access schedule, previously shown to increase motivated behavior following sucrose abstinence, and then underwent either a 0, 7, or 30 day period of abstinence. Next, electrophysiological recording procedures were used to examine NAc activity (n = 199 neurons) during resumption of sucrose self-administration. Results showed no increase in sucrose-seeking or changes in cell firing of NAc neurons following any abstinence period. Furthermore, in a separate group of animals (n = 17) trained under identical conditions, sucrose-seeking behaviors were assessed during extinction and cue-induced reinstatement to further examine if any changes in motivated responding are evident following abstinence. Again, no evidence was obtained for any alterations in sucrose-seeking across abstinence conditions. These results suggest that natural rewards, such as sucrose, when provided in short access, do not always elicit robust changes in motivated responding, or NAc cell firing following abstinence unlike that observed in prior studies with cocaine. These findings are discussed with respect to the role of the NAc in processing goal-directed behaviors for drug vs. natural rewards following periods of abstinence. (c) 2007 Wiley-Liss, Inc.