It has been reported that in the preoptic area endogenous opioid peptidescould inhibit the noradrenaline release in vivo and in vitro. In the presentstudy

receptor autoradiography on the rabbits' brain slices was used to inve-stigate the distribution of 3

H

-etorphine binding sites before and after thedestruction of noradrenaline neurons in n. subcoerulcns and ascending catecho-lamine (CA) axons by 6-hydroxydopamine. The results provide us with mor-phological evidence that 3H-etorphine binding sites before and after thedestruction of noradrenaline neurons in n. subcoerulcns and ascending catecho-lamine (CA) axons by 6-hydroxydopamine. The results provide us with mor-phological evidence that 3

H

-etorphine binding sites in the preoptic area