The effect of anesthetics on the circadian rhythm of rat hippocampal acetylcholine release

背景资料：被认为负责认知、学习和记忆功能的海马乙酰胆碱（ACh）释放在大鼠中显示昼夜节律，即在黑暗（活跃）阶段增加，并且在光照（不活跃）阶段减少。采用微透析技术研究异氟醚麻醉对大鼠海马细胞外乙酰胆碱（ACh）含量昼夜节律的影响，并比较异氟醚麻醉在明相和暗相的影响。在自由活动条件下，以20 min间隔从背侧海马收集透析液，持续60 h以上。采用高效液相色谱法测定透析液中的乙酰胆碱。将年轻雄性大鼠分为三组（每组n=6）：对照组：不给予异氟烷麻醉; DA组：在黑暗（活动）期给予1.4%异氟烷; LA组：在光明（休息）期给予1.4%异氟烷。在自由移动条件下进行体内微透析研究。以20 min间隔从背侧海马收集透析液，持续60 h以上。结果：对照组大鼠海马乙酰胆碱的释放有明显的昼夜变化。在DA组中，异氟醚麻醉后ACh释放的昼夜变化明显中断，而在LA组中异氟醚麻醉没有影响。结论：异氟醚麻醉对海马ACh昼夜节律的影响在活动期比在休息期明显。提示不同时期麻醉对昼夜节律的影响不同。

Background : Hippocampal acetylcholine (ACh) release, accepted as being responsible for cognition, learning and memory functions displays a circadian rhythm in rats, i.e. increases during the dark (active) phase, and decreases during the light (inactive) phase. The aim of the present experiment was to investigate the effect of isoflurane anesthesia on the circadian rhythm of hippocampal extracellular ACh level in rats using microdialysis technique, and compare this effect of isoflurane anesthesia administered during the light phase and that during the dark phase.Methods : Young male rats were used in microdialysis studies. The dialysate was collected from the dorsal hippocampus at 20-min intervals under freely moving conditions for more than 60 h. Acetylcholine in the dialysate was measured by high performance liquid chromatography. The young male rats were divided into three groups (n=6 in each group) : Group Control : isoflurane anesthesia was not administered ; Group DA : 1.4% isoflurane was administered during dark (active) phase ; Group LA : 1.4% isoflurane was administered during light (rest) phase. In vivo microdialysis studies were performed in free moving conditions. The dialysate was collected from the dorsal hippocampus at 20-min intervals for more than 60 h. Acetylcholine in the dialysate was measured by high performance liquid chromatography.Results : The hippocampal acetylcholine release showed clear diurnal change in Group Control. In Group DA, the diurnal change of ACh release was significantly disrupted after isoflurane anesthesia, while isoflurane anesthesia coused no effect in Group LA.Conclusions : The influence of isoflurane anesthesia on the hippocampal ACh circadian rhythm was pronounced when administered during the active phase than that administered during the rest phase. Our finding suggested that anesthesia during different phase might cause different effect on circadian rhythm.