Cerebral blood flow after treatment with ORG-2766, a potent analog of ACTH 4--9.

Regional cerebral blood flows (rCBF) were measured in conscious, male rats at 10, 30, 60 min and 24 hr after intravenous administration of a potent, behaviorally active analog of ACTH/MSH 4--9 (ORG-2766). Flows in the basal ganglia, hippocampus, septal area and frontal cortex were depressed significantly throughout the 60 min postinjection period. HYpothalamic and parietal flows were depressed at 10 and 30 min, but recovered by 60 min, whereas flow to the cerebellum was depressed between 30 and 60 min postinjection. The least changed and therefore relatively better perfused area throughout the first 60 min period was the occipital cortex. By contrast, at 24 hr, when perfusion of all brain regions had returned to near control levels, flow to the occipital cortex was elevated. During the first hour after treatment with either ORG-2766 or alphaMSH the patterns of regional circulation in the brain were qualitatively the same. The data suggest that ORG-2766 and, probably, alpha MSH trigger serially linked neurophysiologic changes in the brain lasting at least 24 hr, which organize the behavioral actions of this class of peptides on memory and attentional processes.