MICROINJECTION OF THE ALPHA-1-AGONIST METHOXAMINE INTO THE PARAVENTRICULAR HYPOTHALAMUS INDUCES ANOREXIA IN RATS

Adrenergic receptors within the paraventricular hypothalamus (PVN) play a prominent role in the control of food intake: stimulation of alpha-2-adrenoceptors induces food intake whereas stimulation of alpha-1-adrenoceptors suppresses food intake. This study further examines the role of PVN alpha-1-adrenoceptors by examining the effects on food and water intake of the alpha-1-adrenergic agonist methoxamine (100, 200, 400 nMol) microinjected into the rat paraventricular hypothalamus. Methoxamine suppressed food intake but not water intake. Doses of 100, 200, and 400 nMol methoxamine suppressed food intake by 47%, 64%, and 96%, respectively. These results further confirm the hypothesis that administration of alpha-1-agonists into the PVN acts to significantly suppress food intake: an action that is in opposition to the facilitory effects of alpha-2-adrenergic agonists on food intake.