Motivational depression associated with norepinephrine-induced eating from the hypothalamus: Resemblance to the ventromedial hyperphagic syndrome

Abstract

Abstract Rats with lateral hypothalamic cannulae were injected with norepinephrine and tested when both hungry and satiated on appetitive tasks of varying difficulty. On a simple consummatory test norepinephrine produced more eating than saline at both 0 and 24 hr of deprivation, and performance at 24 hr was more potentiated than that at 0 hr. On a continuously reinforced lever-pressing task, norepinephrine potentiated pressing only at 0-hr deprivation. When pressing was reinforced on a 30-sec variable interval schedule, norepinephrine potentiated pressing at 0 hr of deprivation, but after 24 hr of deprivation norepinephrine-injected rats pressed significantly less than saline-injected controls. These data suggest that norepinephrine produced a motivational depression in a rat's willingness to work for food which is similar to that seen following ventromedial lesions of the hypothalamus.