| Effects of Halothane, Enflurane or Isoflurane on the m1 or m3 Muscarinic Receptor Expressed in Xenopus Oocytes. |
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Sang Hwan Do |
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Department of Anesthesiology, Seoul National University Medical College, Seoul, Korea. |
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| Abstract |
BACKGROUND
Muscarinic receptors are distributed abundantly in the central nervous system and peripheral visceral organs, and have a close relationship with anesthesia. We investigated the effects of halothane, enflurane or isoflurane on m1 or m3 muscarinic signaling. METHODS: Using two electrode voltage clamps, Ca2+ -activated Cl- currents (ICl(Ca)) were measured in Xenopus oocytes injected with an m1 or m3 receptor mRNA. ICl(Ca) was induced with the application of acetyl beta-methylcholine with or without exposure to volatile anesthetics. RESULTS: Halothane depressed the m1 and m3 receptor function significantly (m1; 0.49 +/- 0.17 microampere -> 0.1 +/- 0.05 microampere, m3; 0.74 +/- 0.2 -> 0.23 +/- 0.06 microampere, P < 0.05).
Enflurane also decreased signaling through both receptors significantly (m1; 0.49 +/- 0.1 -> 0.15 +/- 0.04 microampere, m3; 0.95 +/- 0.34 -> 0.19 +/- 0.05 microampere, P < 0.05). However, while isoflurane depressed m3 signaling significantly (0.82 +/- 0.19 -> 0.3 +/- 0.09 microampere, P < 0.05), it did not cause significant changes in ICl(Ca) through the m1 receptor (0.29 +/- 0.05 vs 0.23 +/- 0.09 microampere, P > 0.5). From a concentration-response curve, enflurane decreased m1 and m3 signaling dose-dependently.
CONCLUSIONS
Our data suggests that m1 and m3 muscarinic receptors were depressed by halothane, enflurane or isoglurane except for the fact that the m1 receptor was not affected by isoflurane. |
| Key Words:
Anesthetics, volatile: enflurane; halothane; isoflurane; Cells: Xenopus oocytes; Receptors: muscarinic |
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