5-HT_1A Receptors Mediate Analgesia Induced by Emulsified Sevoflurane in Thermal Nociception but Have Little Effect on Chemical Nociception

Abstract

Objective: The study aimed to investigate the relationship between the analgesic effect of sevoflurane and 5-serotonin receptor 1A (5-HT_1A R) in the spinal cords of mice. Methods: Analgesic mouse models were established by intraperitoneal injection of emulsified sevoflurane, and the influence of p-MPPF (a specific antagonist of 5-HT_1A Rs) intrathecal injection on the changes in tail-flick latency in tail-withdrawal test, pain threshold in hot-plate test (HPPT), and writhing times in acetic acid-induced writhing test were recorded. Results: Intraperitoneal injection of emulsified sevoflurane alone produced an analgesic effect (p < 0.05). p-MPPF (2, 4, and 8 μg) alone had no impact on tail-flick latency, HPPT, and writhing times in mice (p > 0.05). The 3 doses of p-MPPF reduced the tail-flick latency or HPPT. p-MPPF 8 μg can increase the writhing times (p < 0.05) in analgesic mice with sevoflurane, while p-MPPF 2 and 4 μg did not affect the writhing times. Conclusion: 5-HT_1A Rs in the spinal cord may be an important target for the analgesic effect of sevoflurane on the thermal nociception, but it has little relation to the anti-chemical chemical nociceptive effect of sevoflurane.