5-HT调制离体脊髓运动神经元活动的作用特征

CHARACTERISTICS OF 5-HT MODULATION ON SPINAL MOTONEURON ACTIVITIES 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,观察5-羟色胺(5-HT)对MN活动的影响(n=50)。发现5-HT在78％MN引起伴有膜电导降低的去极化或内向电流,反应在TTX溶液中持续存在,翻转电位在-90～-105mV,为氟苯氧丙胺增强,但被二甲麦角新碱颉颃。5-HT在8％MN诱发超极化反应,但易于失敏。5-HT在40％MN诱导兴奋和(或)抑制性突触活动,分别对犬尿烯酸和士的宁敏感。结果表明5-HT通过直接或间接方式对MN活动产生兴奋或抑制性调制作用。

Membrane potential and current recordings were intracellularly made from the antidromically identified motoneurons(MNs) in the transverse thoracolumbar spinal cord slices isolated from neonate rat . Superfusion(10-100umol/L) or pressure ejection of serotonin( 5-HT) produced a slow depolarization (inward current ) with decrease of membrane conductance and reversal potential of -90 to -105m V in 78% of MNs testcd(n = 50). The depolarization or inward current was persistent in TTX-containing solution, and enhanced by fluoxctine (1-5 umol/L) but antagonized by methyscrgide(1-10umol/L) or cyprohcptadine (10-30umol/ L). In 8% MNs, a hyperpolarization with decrease of membrane resistance was induced by 5-HT, exhibiting an excessive tachyphylaxis property. The spontaneous synaptic activities were also evoked by 5-HT in 40% MNs, including TTX-sensitive excitatory or inhibitory potential which was eliminated by kynureriic acid (0.5-1mmol/L) or strychnine (1umol / L), respectively. The results suggest that 5-HT directly or indirectly modulates MN activities in the neonate rat spinal cord slices.