Opiate receptors: enkephalins and endorphins.

Journal article

Opiate receptors in the central nervous system may be classified according to pharmacological, behavioural, or binding studies. Classical mu-receptors probably have beta-endorphin as an endogenous ligand, and seem to be involved in the modulation of pain perception, low-frequency acupuncture analgesia, and the stimulation of prolactin, growth hormone and thyroid-stimulating hormone release. Met-enkephalin is likely to be an endogenous ligand for the delta-receptors, which predominate in the basal ganglia and limbic systems; such receptors may tonically inhibit the release of corticotrophin-releasing factor. It has been suggested that the newly-described kappa-receptors may inhibit the release of vasopressin and gonadotrophin-releasing factor; dynorphin may be their endogenous ligand. Endogenous opiates controlling cardiovascular and respiratory reflexes are likely to activate mu-receptors, while high-frequency acupuncture may alleviate the symptoms of opiate withdrawal by allowing an increase in Met-enkephalin to activate delta-receptors. In the periphery, beta-endorphin is concentrated in the corticotrophs of the anterior pituitary, and is cosecreted with ACTH and related peptides. Circulating Met-enkephalin originates in the gut, sympathetic nervous system and adrenal medulla. Met-enkephalin may also be extracted from carcinoid tumours and phaeochromocytomas. Elevations in circulating Met-enkephalin may occur in certain disease states with cardiovascular and psychiatric manifestations. However, manipulation of endogenous or exogenous opiates has as yet no certain place in any clinical situation.

Authors: Grossman, A; Clement-Jones, V

• Publication status: Published
• Journal: Clinics in endocrinology and metabolism
• Volume: 12
• Issue: 1
• Pages: 31-56
• Publication date: 1983-03-01
• DOI: 10.1016/S0300-595X(83)80028-0
• ISSN: 0300-595X
• Language: English
• Keywords: Acupuncture Therapy; Brain Diseases; Mental Disorders; Cardiovascular Physiological Phenomena; Respiration; Pain; Prolactin; Neoplasms; Adrenocorticotropic Hormone; Hypothalamo-Hypophyseal System; Humans; Growth Hormone; Enkephalins; Thyrotropin; Endorphins; Receptors, Opioid