The effect of intragastric ethanol on meal size in the rat.

Although ethanol is a calorically dense substance, little is known about the mechanisms by which those calories are detected, nor how they effect subsequent intake of other calories. In the current study, four doses of ethanol (0, 1, 2, and 3.5 g/kg) were administered to rats prior to 30-min access to a sucrose solution. The effect of ethanol (EtOH) to impact sucrose intake was compared to that of another carbohydrate, glucose, matched for calories, and to NaCl solutions matched to the osmotic properties of the glucose. A final set of conditions provided calories in the form of EtOH as well as osmoles in the form of NaCl to match the combined caloric and osmotic properties of the glucose solutions. Aqueous solutions of EtOH and of glucose suppressed food intake in a dose-dependent fashion with glucose tending to be more effective than EtOH. NaCl in water did not suppress intake. Surprisingly, when NaCl was added to the EtOH solution the effect of EtOH to suppress food intake was completely ameliorated. Subsequent analysis of plasma EtOH levels showed that adding NaCl also reduced the rate at which EtOH appeared in the plasma. The results suggest that changes of short-term food intake caused by EtOH calories are produced by different inhibitory signals than those produced by other carbohydrates. While other carbohydrates generate preabsorptive signals within the stomach, ethanol appears to have to leave the stomach to inhibit further food intake.