5-羟色胺抑制离体脊髓运动神经元的突触传递

SUPPRESSION OF SYNAPTIC TRANSMISSION TO SPINAL MOTONEURONS BY 5-HYDROXYTRYPTAMINE IN VITRO

应用新生大鼠脊髓切片运动神经元(MN)细胞内记录技术,发现5-羟色胺(5-HT)10～100μmol/L灌流可浓度依从地抑制背、腹根刺激在MN诱发的兴奋性突触后电位(EPSP)和抑制性突触后电位,但可增大外源性谷氨酸引起的MN去极化。5-HT对背根性EPSP的抑制无刺激频率依赖性,可为5-HT_(1A)受体激动剂8-OH-DPAT模拟,但不受士的宁、酮色林及MDL 72222的影响。结果表明5-HT可直接激活初级传入纤维末梢5-HT_(1A)受体而抑制MN的突触传递。

With the intracellular recording techniques, effects of 5-hydroxytryptamine (5-HT) on synaptic transmission to motoneurons (MNs) were studied in the neonate rat spinal cord slices. It was found that superfusion with 5-HT (10-100 μmol/L) suppressed dose-dependently both the excitatory (EPSP) and inhibitory (IPSP) postsynaptic potentials evoked by dorsal or ventral root stimulation, while increased the exogenous glutamate-induced depolarization. The inhibitory action of 5-HT on dorsal root-EPSPs was neither nullified by increasing stimulus frequency nor eliminated by strychnine (1 μmol/ L), ketanserin (1 μmol/ L) and MDL 72222 (10 μmol/ L), but mimicked by 8-OH-DPAT (1-10 μmol/L). The results suggest that the 5-HT suppression of synaptic transmission to MNs is possibly mediated directly by activation of 5-HTIA receptor on primary afferent synapses to the MNs.