title: Endogenous morphine modulates acute thermonociception in mice.
abstract: The endogenous synthesis of morphine has been clearly demonstrated throughout the phylogenesis of the nervous system of mammals and lower animals. Endogenous morphine, serving as either a neurotransmitter or neurohormone, has been demonstrated in the nervous system of both vertebrates and invertebrates. As one of the effects of exogenous morphine is the modulation of pain perception, we investigated the effects that the depletion of endogenous morphine had on nociceptive transmission. The immunoneutralization of endogenous morphine from brain extracellular spaces was obtained through the intracerebroventricular administration of affinity purified anti-morphine IgG to mice, which then underwent the hot plate test. Endogenous morphine immunoneutralization decreased thermal response latency and attenuated the anti-nociceptive effect of the mu selective agonist DAMGO in hot plate test suggesting that endogenous morphine is involved in pain modulation.
authors.affiliation: Neuroscience Research Institute, State University of New York, USA.
authors.forename: M
authors.initials: M
authors.lastname: Guarna
authors.forename: E
authors.initials: E
authors.lastname: Bianchi
authors.forename: A
authors.initials: A
authors.lastname: Bartolini
authors.forename: C
authors.initials: C
authors.lastname: Ghelardini
authors.forename: N
authors.initials: N
authors.lastname: Galeotti
authors.forename: L
authors.initials: L
authors.lastname: Bracci
authors.forename: C
authors.initials: C
authors.lastname: Neri
authors.forename: D
authors.initials: D
authors.lastname: Sonetti
authors.forename: G
authors.initials: G
authors.lastname: Stefano
mesh_terms: D000208:Acute Disease; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D002021:Buffers; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000494:pharmacology; D016314:Ethylketocyclazocine / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D006930:Hyperalgesia / Q000188:drug therapy / Q000378:metabolism*; D007074:Immunoglobulin G / Q000032:analysis / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009020:Morphine / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D009043:Motor Activity; D009619:Nociceptors / Q000378:metabolism; D018847:Opioid Peptides / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D012881:Skin Temperature
chemical_list: D000701:Analgesics, Opioid; D002021:Buffers; D007074:Immunoglobulin G; D018847:Opioid Peptides; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D016314:Ethylketocyclazocine; D009020:Morphine; D020881:Enkephalin, D-Penicillamine (2,5)-