title: Muscarinic receptor subtypes modulate the release of [3H]-noradrenaline in rat spinal cord slices.
abstract: Spinal muscarinic receptors are involved in the mediation of antinociceptive effects. The modulation of noradrenaline (NA) release on muscarinic receptor subtypes in the rat spinal cord was investigated in in vitro perfusion experiments. After rat spinal cord slices were preincubated in [3H]NA, the slices were perfused with a superfusion apparatus. The slices were field stimulated during the 4th (S1) and 11th (S2) superfusion collection periods. Perfusion of drugs was initiated at the 8th collection period and was maintained until the 14th collection period. Fractional release was calculated as the percentage of the radioactivity present in the slices at the beginning of the stimulation period. Drugs were administered between S1 and S2. The following drugs were used: [3H]NA, neostigmine, pirenzepine (M1 antagonist), AFDX116 (M2 antagonist), atropine. Neostigmine significantly increased the release of [3H]NA in a concentration-dependent manner. Pirenzepine (1 microM) and atropine (0.3 microM) significantly reduced the release of [3H]NA, but AFDX116 (1 microM) did not significantly reduce release in the presence of neostigmine (1 microM). The results of this study indicate that neostigmine can enhance noradrenergic neurotransmission, and that acetylcholine can stimulate spinal cord NA release via M1 muscarinic receptor subtypes.
authors.affiliation: Department of Anesthesiology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan. eume@ndmc.ac.jp
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Umeda
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Aramaki
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Mori
authors.forename: Tomiei
authors.initials: T
authors.lastname: Kazama
mesh_terms: D000818:Animals; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D066298:In Vitro Techniques; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009388:Neostigmine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium / Q000378:metabolism
chemical_list: D002800:Cholinesterase Inhibitors; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D014316:Tritium; D009388:Neostigmine; D009638:Norepinephrine