甘丙肽对幼年大鼠蓝斑神经元兴奋性的影响及作用机制

Effect and function mechanism of Galanin on neonatal rat locus coeruleus neurons

目的探讨甘丙肽(galanin,GAL)对幼年大鼠蓝斑神经元兴奋性的影响,研究甘丙肽与其受体(GalR)和钾离子通道的作用机制。方法制备幼年大鼠脑片,采用全细胞记录法记录灌流给予甘丙肽后,蓝斑神经元静息膜电位水平和自发动作电位的发放频率;灌流给予不同浓度甘丙肽2型受体(GalR2)激动剂AR-M1896和不同类型钾离子通道阻断剂后,研究甘丙肽对幼年大鼠蓝斑神经元兴奋性的影响。结果甘丙肽能够诱导蓝斑神经元膜电位发生超级化并抑制其动作电位的发放,但GalR2激动剂AR-M1896只有在高浓度(1μM)时才能够诱导蓝斑神经元膜电位发生轻微的超级化并减少动作电位的发放;电压依赖性钾通道阻断剂四乙胺(Tetraethylammonium,TEA)能够部分阻断甘丙肽的抑制作用,内向整流钾通道阻断剂Ba Cl2能够显著阻断甘丙肽的抑制作用,而其他钾通道阻断剂,如ATP敏感性钾通道阻断剂格列本脲(Glybenclamide)、大电导钙依赖的钾通道(BK通道)阻断剂北非蝎毒素(Charybdotoxin)、小电导钙依赖的钾通道(SK通道)阻断剂蜂毒明肽(Apamin)均未能阻断甘丙肽的抑制作用。结论甘丙肽能够抑制幼年大鼠蓝斑神经元的兴奋性,其抑制作用可能主要是通过甘丙肽1型受体(GalR1)产生的,并且这种抑制作用可能与TEA敏感的钾通道和内向整流钾通道相关,而ATP敏感的钾通道和钙依赖的钾通道不参与其中。

Objective To explore the effect of galanin（ GAL） on locus coeruleus（ LC） neurons from neonatal rat and mechanism with its receptor GalR and potassium channel. Methods Brain slices from neonatal rats were prepared and the resting membrane potential and spontaneous action potential of LC neurons were recorded with whole cell patch-clamp configuration. GAL,AR-M1896 and potassium channel blockers were bath applied with different concentration. Results Bath application GAL induced hyperpolarization and inhibited firing rate of LC neurons. However,AR-M1896（ a selective GalR2 agonist） did not induce significant effect on LC neurons,only at very high concentration（ 1 μM） it induced slight hyperpolarization and reduced firing rate. The inhibitory effect of GAL was partially blocked by TEA（ an antagonist of voltage-dependent potassium channel） and significantly blocked by Ba Cl2（ an antagonist of inward-rectifying potassium channels）,while other potassium channels blockers such as Glybenclamide（ ATP-sensitive potassium channel blocker）,Charybdotoxin（ large-conductance Ca2 ＋-activated K＋channels blocker）,Apamin（ small-conductance Ca2 ＋-activated K＋channels blocker） failed to block it. Conclusion GAL inhibits LC neurons from neonatal rats,mainly through GalR1. TEA-sensitive potassium channels and inward-rectifying potassium channels,but not ATP-sensitive potassium channel and calcium-activated potassium channel,are involved in this inhibition.