Microinjections of dopaminergic agents in the nucleus accumbens affect ethanol consumption but not palatability.

It was determined whether ethanol palatability in rats could be changed by manipulating the reinforcement experienced during limited access consumption. During the first 3 days of the experiment, initial taste reactivity (TR) testing to distilled water (1 day) and 10% alcohol (2 days) was performed. Following the establishment of baseline TR, separate groups of animals received bilateral microinjections (0.5 microl/side) into the nucleus accumbens of either the nonspecific dopamine agonist d-amphetamine sulfate (20 microg, n = 10), the D(2) antagonist raclopride (1.0 microg, n = 8), or physiological saline (n = 5). The injections occurred at the same time each day for 5 consecutive days. Five minutes after the microinjection, the fluid-deprived rats were given 30-min access to 10% ethanol. Over the 3 days following drug administration, TR to distilled water and 10% alcohol was repeated. After this, the rats were once again given 30 min of access to 10% ethanol for 5 consecutive days, but without drug microinjection prior to alcohol access. A final TR exposure (the same as the others) was performed over the final 3 days of the study. Both raclopride and d-amphetamine administration produced reductions in ethanol consumption (in comparison to saline treatment). However, treatment with d-amphetamine and raclopride during ethanol consumption did not cause significant, conditioned changes in palatability as measured by the taste reactivity procedure. These results suggest that dopamine plays a role in the motivation to consume ethanol but this neurotransmitter is not involved in evaluating its incentive value.