Strychnine-sensitive glycine receptors mediate the analgesic but not hypnotic effects of emulsified volatile anesthetics

The present study was designed to investigate the role of strychnine-sensitive glycine receptors in hypnosis and analgesia induced by emulsified volatile anesthetics. After having established the mice model of hypnosis and analgesia by intraperitoneally injecting (i.p.) appropriate doses of ether, enflurane, isoflurane or sevoflurane, we intracerebroventricularly (i.c.v.) or intrathecally (i.t.) injected different doses of strychnine and then observed the effects on the sleeping time using the awaken test and the pain index in hot-plate test (HPPI) using the hot-plate test. In the awaken test, strychnine 1, 2, 4 mu g (i.c.v.) had no distinctive effect on the sleeping time of the mice treated with the four emulsified inhalation anesthetics mentioned above (p > 0.05); in the hot-plate test, strychnine 0.1, 0.2, 0.4 mu g (i.t.) can significantly and dose-dependently decrease the HPPI of the mice treated with emulsified ether, enflurane and sevoflurane (p < 0.05, p < 0.01); strychnine 0.1 mu g (i.t.) did not affect the HPPI of the mice treated with emulsified isoflurane (p > 0.05), but 0.2 and 0.4 mu g (i.t.) can significantly decrease the HPPI of the mice treated with emulsified isoflurane (p < 0.05, p < 0.01). These results suggest that strychnine-sensitive glycine receptors may contribute to the analgesic but not to the hypnotic effects induced by ether, enflurane, isoflurane and sevoflurane. Copyright c 2007 S. Karger AG, Basel.