Beck S G, Choi K C
Department of Pharmacology, Loyola University Chicago, Stritch School of Medicine, Maywood, IL 60153.
Neurosci Lett. 1991 Nov 25;133(1):93-6. doi: 10.1016/0304-3940(91)90065-2.
The firing rate of hippocampal pyramidal cells recorded from the CA3 subfield is inhibited by 5-hydroxytryptamine (5-HT, serotonin) or by electrical stimulation of the ascending serotonergic fibers from the raphe. The mechanism of action of this inhibitory effect produced by 5-HT has not been determined. Intracellular recording techniques in the hippocampal slice preparation were used to measure the effect of 5-HT perfusion on membrane properties of CA3 pyramidal cells. In 15 out of 16 cells tested, 5-HT elicited a pronounced hyperpolarization concomitant with a decrease in membrane resistance. The hyperpolarization was not altered with either potassium chloride or potassium methylsulphate electrodes; the hyperpolarization by 5-HT was not present when electrodes were filled with cesium chloride. The reversal potential of the 5-HT mediated response was determined to be-105.5 mV in 3 mM KCl buffer using single electrode voltage clamp techniques. Based on these results we conclude that the mechanism of action of the 5-HT inhibition of CA3 hippocampal pyramidal cell excitability is due to an increase in potassium conductance.
从CA3亚区记录的海马锥体细胞的放电频率受到5-羟色胺（5-HT，血清素）或来自中缝的升支血清素能纤维的电刺激的抑制。5-HT产生这种抑制作用的作用机制尚未确定。采用海马脑片制备中的细胞内记录技术来测量5-HT灌注对CA3锥体细胞膜特性的影响。在测试的16个细胞中的15个中，5-HT引起明显的超极化，同时膜电阻降低。使用氯化钾或甲基硫酸钾电极时，超极化没有改变；当电极填充氯化铯时，不存在5-HT引起的超极化。使用单电极电压钳技术在3 mM KCl缓冲液中测定5-HT介导反应的反转电位为-105.5 mV。基于这些结果，我们得出结论，5-HT抑制海马CA3锥体细胞兴奋性的作用机制是由于钾电导增加。
