title: Colocalization and shared distribution of endomorphins with substance P, calcitonin gene-related peptide, gamma-aminobutyric acid, and the mu opioid receptor.
abstract: The endomorphins are endogenous opioids with high affinity and selectivity for the mu opioid receptor (MOR, MOR-1, MOP). Endomorphin-1 (Tyr-Pro-Trp-Phe-NH(2); EM1) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2); EM2) have been localized to many regions of the central nervous system (CNS), including those that regulate antinociception, autonomic function, and reward. Colocalization or shared distribution (overlap) of two neurotransmitters, or a transmitter and its cognate receptor, may imply an interaction of these elements in the regulation of functions mediated in that region. For example, previous evidence of colocalization of EM2 with substance P (SP), calcitonin gene-related peptide (CGRP), and MOR in primary afferent neurons suggested an interaction of these peptides in pain modulation. We therefore investigated the colocalization of EM1 and EM2 with SP, CGRP, and MOR in other areas of the CNS. EM2 was colocalized with SP and CGRP in the nucleus of the solitary tract (NTS) and with SP, CGRP and MOR in the parabrachial nucleus. Several areas in which EM1 and EM2 showed extensive shared distributions, but no detectable colocalization with other signaling molecules, are also described.
authors.affiliation: Neuroscience Program, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA.
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Greenwell
authors.forename: Sheryl
authors.initials: S
authors.lastname: Martin-Schild
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Inglis
authors.forename: James E
authors.initials: JE
authors.lastname: Zadina
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism*; D018847:Opioid Peptides / Q000378:metabolism; D010146:Pain / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*; D014018:Tissue Distribution; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; D018847:Opioid Peptides; D017450:Receptors, Opioid, mu; C105293:endomorphin 1; D013373:Substance P; C105294:endomorphin 2; D005680:gamma-Aminobutyric Acid; D015740:Calcitonin Gene-Related Peptide