title: The spinal muscarinic receptor subtypes contribute to the morphine-induced antinociceptive effects in thermal stimulation in mice.
abstract: The present study was undertaken to clarify how spinal muscarinic receptors can be involved in the antinociceptive effects induced by morphine in thermal stimulation. The morphine-induced antinociceptive effects (26.6 micromol/kg, s.c.) was inhibited by an intrathecal (i.t.) injection of the muscarinic antagonist (M) atropine and the M(1)/M(4) antagonist pirenzepine in a dose-dependent manner. In contrast, the M(2) antagonist methoctramine and the M(3) antagonist 4-DAMP did not inhibit the morphine-induced antinociceptive effects. Injection (i.t.) of the putative M(1) agonist McN-A-343 resulted in dose-dependent antinociceptive effects in thermal stimuli. In addition, antinociceptive effects induced by the i.t. injection of morphine were not inhibited by the M(1)/M(4) antagonist pirenzepine, although pirenzepine did inhibit the intracerebroventricular (i.c.v.) injection of morphine-induced antinociceptive effects. These results suggest that the morphine-induced antinociceptive effects in thermal stimuli are regulated by the M(1) or M(4) receptor in the spinal cord.
authors.affiliation: Department of Physiology and Pharmacology, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Honda
authors.forename: Suguru
authors.initials: S
authors.lastname: Ando
authors.forename: Kohei
authors.initials: K
authors.lastname: Koga
authors.forename: Yukio
authors.initials: Y
authors.lastname: Takano
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D043643:Receptor, Muscarinic M1 / Q000502:physiology; D011976:Receptors, Muscarinic / Q000145:classification* / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology
chemical_list: D000700:Analgesics; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic; D009020:Morphine