Intracerebroventricular injection of ostrich beta-endorphin to satiated pigeons induces hyperphagia but not hyperdipsia.

Satiated pigeons received intracerebroventricular injections of either ostrich (0.06, 0.3 and 1.5 nmoles) or human (0.06 and 1.5 nmoles) beta-endorphin, or a control solution, and their consumption of food and water was monitored during the half hour after these treatments. At each administered dose, ostrich beta-endorphin enhanced food without altering water intake. By contrast, human beta-endorphin did not induce any reliable alteration either of feeding or drinking. Together with previous studies performed in pigeons with opiate antagonists, these results suggest that the feeding system of pigeons is modulated by an endorphinergic mechanism. By contrast, no evidence exists so far that such a mechanism operates for controlling drinking, as appears to be the case in mammals.