Nicotinic acetylcholine receptors mediate the hypnotic and analgesic effects of emulsified inhalation anesthetics

This study was designed to investigate the role of nicotinic acetylcholine receptors (nAChRs) in hypnosis and analgesia induced by emulsified inhalation anesthetics. After having established the mice model of hypnosis and analgesia by intraperitoneal injections of appropriate doses of enflurane, isoflurane or sevoflurane, we intracerebroventricularly or intrathecally injected different doses of nicotine and then observed the effects on the sleeping time using awaken test and the pain threshold in hot-plate test (HPPT) using hot-plate test. In the awaken test, 10, 20 and 40 μg of nicotine (intracerebroventricularly) significantly decreased the sleeping time of the mice treated with the three emulsified inhalation anesthetics mentioned above ( P  <   0.05 or 0.01). In the HPPT, 5, 10 and 15 μg of nicotine (intrathecally) did not affect the HPPT in conscious mice ( P  >   0.05); in contrast, 5, 10 and 15 μg of nicotine (intrathecally) significantly decreased the HPPT of the mice treated with emulsified inhalation anesthetics ( P  <   0.05 or 0.01). The data presented in this study suggest that nAChRs may be important targets for the hypnotic and analgesic effects induced by emulsified enflurane, isoflurane and sevoflurane.