Pattern of drinking and feeding produced by hypothalamic norepinephrine injection in the satiated rat

Injection of norepinephrine into the perifornical region of the anterior hypothalamus elicited both drinking and feeding in satiated rats. Analysis of these behaviors revealed the following: (1) Both responses were dose-dependent, occurring at doses at least as low as 0.5 mug. (2) The drinking response (1-4 ml) had a latency of around 1.5 min and a duration of 2-3 min. It was followed within a minute or two by eating (2-4 g) that lasted approximately 20 min. It was also followed by a period of drinking suppression that lasted approximately 60 min. (3) Satiation from the ingestion process appeared to be a primary factor in terminating the elicited feeding response, whereas a time-related factor was important in terminating the elicited drinking. (4) These ingestive responses produced by noradrenergic stimulation of the anterior perifornical hypothalamus were found to bear striking similarities to the rat's natural feeding behavior and premeal component of his natural food-associated drinking behavior. (5) These noradrenergically elicited responses could not be observed with lateral hypothalamic stimulation, while only feeding was elicited by ventromedial hypothalamic stimulation. (6) The drinking induced by central noradrenergic stimulation, in contrast to that induced by peripheral beta-adrenergic stimulation, was unaffected by nephrectomy.