Opposite effects on the ingestion of ethanol and sucrose solutions after injections of muscimol into the nucleus accumbens shell

Abstract

Injection of the GABA(A) receptor agonist muscimol into the nucleus accumbens shell (AcbSh) elicits robust feeding in satiated rats, but has no effect on water intake. The current study was designed to examine whether intra-AcbSh muscimol injections influence the intake of ethanol solutions in rats trained to drink using a limited access paradigm. We confirmed that bilateral injections of muscimol (100 ng) into the AcbSh produce large increases in the intake of sucrose solutions and of the chow maintenance diet but found in two independent experiments that these injections potently reduce the intake of a 10% ethanol solution. Furthermore, intra-AcbSh muscimol significantly increased intake of an ethanol-sucrose mixture. These results demonstrate that activating GABA(A) receptors in the vicinity of the AcbSh can have opposite effects on the intake of different caloric substances and are consistent with the possibility that GABAergic circuits in the AcbSh may play a role in mediating voluntary ethanol intake.

Fig. 1

Schematic representation of a typical bilateral AcbSh injection site. (AcbC: nucleus accumbens core; CPu: caudate-putamen)

Fig. 2

Experiment 1: Effects of intra-AcbSh injections of saline or muscimol (100 ng/side) on the mean 60 min intakes of a 10% ethanol solution, a 10% sucrose solution, or lab chow. * = p < .001 vs. saline injections

Fig. 3

Experiment 2: Effects of intra-AcbSh injections of saline or muscimol (100 ng/side) on the 60 min consumption of a 10% ethanol solution, a 10% sucrose solution, or a solution containing 10% ethanol and 10% sucrose expressed as a) mean total volume ingested, b) mean dose of ethanol ingested, and c) mean total caloric intake. * = p < .001 vs. saline injections.