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Koshizaki M, Kawamata M, Shimada SG, Saito Y, Collins JG: 5-HT3 receptors partially mediate halothane depression of spinal dorsal horn sensory neurons. Anesth Analg. 2003 Apr;96(4):1027-31
We recently reported that gamma-aminobutyric acid type A- and strychnine-sensitive glycine receptor systems partially mediate halothane depression of spinal dorsal horn low-threshold neurons. Serotonin subtype 3 (5-HT (3)) receptors belong to the same ligand-activated ion-channel family as gamma-aminobutyric acid type A- and strychnine-sensitive glycine receptors, so we examined the possible involvement of 5-HT receptor systems in halothane depression of spinal sensory neurons. Extracellular recordings of spinal low-threshold neurons were obtained in decerebrate, spinally transected rats. Receptive field size and brush-induced activity were recorded in the presence or absence of 5-HT antagonists and in the presence or absence of 1.1% (1 minimum alveolar anesthetic concentration) halothane. In the absence of halothane, antagonists had no effect on receptive field size or brush-induced activity. In the presence of halothane, methysergide, a nonselective 5-HT antagonist, and tropisetron, a selective 5-HT (3) antagonist, significantly reversed the halothane-induced reduction in receptive field size but did not alter halothane depression of brush-induced activity. Methiothepin, a 5-HT (1) antagonist, and ketanserin, a 5-HT (2) antagonist, did not reverse halothane depression. These results support the hypothesis that 5-HT (3) receptors partially mediate some inhibitory effects of halothane on spinal dorsal horn neurons. IMPLICATIONS: The results of this study support the hypothesis that halothane depression of spinal sensory neuronal responses to low-intensity stimuli is mediated, to a minor extent, by serotonin subtype 3 neurotransmitter systems. |
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