Hypothalamic deafferentation in the rat appears to discriminate between the anterior lobe and intermediate lobe response to stress.

Anterolateral deafferentation of the mediobasal hypothalamus prevented the increase of the plasma corticosterone concentration induced by ether, histamine and electric footshock. Hypothalamus deafferentation also prevented the ether stress-induced increase of the plasma levels of ACTH and beta-endorphin immunoreactivity (ACTHi, beta-ENDi). Infusion of isoproterenol evoked an increase of the plasma levels of corticosterone, ACTHi, beta-ENDi and alpha-MSH immunoreactivity (alpha-MSHi) in sham-operated rats. In rats with a deafferented hypothalamus, the responses of plasma corticosterone and ACTHi to isoproterenol were blocked but the responses of plasma beta-ENDi and alpha-MSHi remained intact. We conclude that circulating beta-ENDi after exposure to ether is of anterior lobe origin while circulating beta-ENDi after infusion of isoproterenol is of intermediate lobe origin.