Effects of Blood-Borne Endorphin and Other POMC-Derived Peptides on Brain Functions in Man

Abstract

Hormones of the hypothalamus-pituitary adrenal (HPA) axis are released into the blood as part of the organism’s response to stressful stimuli. These hormones do not only act on peripheral tissues but feed back to the central nervous system, thus forming part of an afferent humoral system modulating a great variety of brain functions, including functions not directly related to the endocrine regulation such as sensory processing and sleep (Fig. 1). In rats, the systemic administration of the proopiomelanocortin (POMC) peptides ACTH 4–10 and β-endorphin has been shown to delay extinction of conditioned avoidance behavior and to affect the hippocampal θ rhythm (de Wied and Jolles 1982; de Wied et al. 1978; Urban and de Wied 1976). Receptors located at the blood— brain barrier and in the circumventricular organs are possible mediators of the central effects of these hormones after peripheral administration (see, e.g., Meisenberg and Simmons 1983; van Houten and Posner 1983).

This work was supported by a grant from the Deutsche Forschungsgemeinschaft (to H.L.F.). The study was approved by the committee on Research Involving Human Subjects of the University of Ulm.