Topographic studies of the effects of microinjections of muscimol on the hypothalamic control of feed intake in sheep.

Ten sheep were used to define the anatomical basis for the feeding systems sensitive to gamma-aminobutyric acid, by using intrahypothalamic microinjections of the gamma-aminobutyric acid agonist, muscimol. In satiated sheep, 1 microL of muscimol (0.5 nmol/microL) elicited feeding when injected into paraventricular, ventromedial, and anterior hypothalamic areas. Similar injections into 39 sites tested in 6-h fasted sheep failed to decrease feed intake. The data suggest that neurons sensitive to gamma-aminobutyric acid in medial hypothalamus may be involved in the initiation of feeding.