ALPHA-2-ADRENOCEPTOR BLOCKADE DOES NOT BLOCK FEEDING INDUCED BY NEUROPEPTIDE-Y IN SHEEP

We tested the hypothesis that blockade of central α2-adrenergic receptors would prevent neuropeptide Y (NPY)-induced feeding. Nine young female sheep were fitted with lateral ventricular cannulas. Bolus intracerebroventricular (ICV) injection of 3 nmol of NPY increased feed intake after 30 min between 45 and 153% in three experiments. A bolus ICV injection of 400 or 100 nmol of the α2-antagonist, yohimbine, either 5 or 30 min before NPY injection, did not attenuate this response. Instead, yohimbine increased feed intake over NPY-induced feeding by 52 to 55%. We interpret these data as evidence that the putative NPY feeding pathway in feed-sated sheep is not dependent on the type of α2-adrenergic mechanism which can be blocked by ICV injection of yohimbine. © 1990.