Microstructural analysis of the effects of THIP, a GABAA agonist, on voluntary ethanol intake in laboratory rats

The effects of GABAA agonist THIP on the acquisition of voluntary ethanol intake and the pattern of food and water consumption were examined through the use of a computer-controlled data acquisition system. Twenty male Long-Evans rats were randomly assigned to two groups, one of which received THIP (16 mg/kg, IP) and the other an equal volume of saline. Subjects were presented with a free choice of ethanol and water immediately following drug injections, which occurred every other day. The initial concentration of ethanol presented was 2% and was increased by increments of 2% following the second presentation of each concentration, up to a maximum concentration of 10%. Subjects treated with THIP consumed significantly greater amounts of ethanol than did saline controls. A microstructural analysis of bout patterns suggested that the increased consumption of ethanol was a function of an increase in the size, duration, and frequency of ethanol drinking bouts. Food intake was also attenuated by THIP treatment. The results indicated that the decrease in total food intake was a function of a decrease in the frequency of the food bouts. However, in contrast to that observed for ethanol intake, the size and duration of the food bouts were unchanged. The qualitatively different patterns in the microstructure of consummatory behavior for ethanol and food following THIP treatment would suggest that differential mechanisms may mediate the food and ethanol effects observed in the present study. In addition, the differential effects of THIP on ethanol consumption relative to water would suggest that GABAA manipulations may play a role in influencing the acquisition of voluntary ethanol drinking.