Ethanol polydipsic choice: effects of alternative fluid polydipsic history.

Two groups of rats drinking either 5% ethanol or 0.9% NaCl solution under a fixed-time 1-min schedule of food pellet delivery became polydipsic during daily 3-hr sessions. When both fluids were made available to animals during sessions, strong side preferences typically developed so that neither fluid was preferred in spite of the fact that one group had a mild-to-moderate physical dependence on ethanol. The group that drank 0.9% NaCl solution initially failed to acquire a strong 5% ethanol polydipsia when this became the sole available fluid, and special procedures were required to induce an ethanol polydipsia comparable to that of the other group. Hence, a history of 0.9% NaCl solution polydipsia interfered with the institution of chronic, ethanol overdrinking in this group. Equal ethanol intakes were maintained in the groups when a compound solution consisting of 5% ethanol plus 0.9% NaCl solution was available along with a 5% ethanol choice. Whenever a 0.9% NaCl solution was presented in competition with either 5% ethanol or the compound 5% ethanol plus 0.9% NaCl solution, ethanol intake was reduced. Implications for the prevention and amelioration of human ethanol overdrinking are discussed.