Ethanol-mediated appetitive conditioning in infant rats, but not corticosterone release, is dependent on route of ethanol administration.

A recent study found appetitive reinforcement in infant rats given 1.0 but not 2.0 g/kg ethanol and only when ethanol was delivered intragastrically (i.g., but not if intraperitoneally, i.p.; Nizhnikov, Pautassi, Truxell, & Spear [2009] Alcohol 43, 347-358). Corticosterone release could modulate ethanol's motivational effects. The goal of this study was to replicate the differential capability of i.g. vs. i.p. ethanol to induce conditioning and to find hormonal correlates underlying this phenomenon. Experiment 1 confirmed that 1.0 g/kg ethanol induced conditioned preference in infant rats when given i.g. but not i.p. In Experiment 2 corticosterone was assessed at 20, 40, 60, or 120 min after ethanol (0.0, 0.5, 1.0, and 2.0 g/kg, i.g. or i.p.). Route of administration failed to alter corticosterone release. The 2.0 g/kg, but not 0.5 or 1.0 g/kg, ethanol dose evoked heightened corticosterone release. The results confirm the differing motivational effects associated with i.g. and i.p. ethanol. These effects do not seem to be related to differential corticosterone responsiveness.