title: Maturation of endomorphin-2 in the dorsal horn of the medulla and spinal cord of the rat.
abstract: The endomorphins are potent and selective endogenous agonists at the mu opioid receptor. We describe here the postnatal ontogeny of endomorphin-2 like immunoreactivity (EM2-LI) in the dorsal horn of the rat medulla and spinal cord. EM2-LI is dense in the superficial lamina of the dorsal horn of the adolescent and adult rat, with fibers also present in skin and dorsal root ganglia. No staining was noted at 3 days of age or younger. Faint and limited staining was noted by 7 days of age. The density and distribution of the immunoreactivity increased with age, reaching an adult-like distribution by 21 days of age. Stress-induced responses mediated by endogenous opioids occur late in development and may be related to the late appearance of endomorphin-2.
authors.affiliation: Department of Psychology, Hunter College, City University of New York, NY 10021, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Barr
authors.forename: J E
authors.initials: JE
authors.lastname: Zadina
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism*; D005727:Ganglia, Spinal / Q000378:metabolism; D007150:Immunohistochemistry; D008526:Medulla Oblongata / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D012867:Skin / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; C105294:endomorphin 2