Perrier Jean-François, Hounsgaard Jørn
Department of Medical Physiology, Panum Institute, University of Copenhagen, DK 2200 Copenhagen N, Denmark.
J Neurophysiol. 2003 Feb;89(2):954-9. doi: 10.1152/jn.00753.2002.
The effects of serotonin (5-HT) on intrinsic properties of spinal motoneurons were investigated with intracellular recordings in a slice preparation from adult turtles. In 55% of the cells that were recorded, addition of 5-HT to the extracellular medium promoted plateau potentials as revealed by the response to depolarizing current pulses applied through the intracellular electrode. In the remaining 45% of cells, 5-HT had an inhibitory effect. However, when tested with an applied electric field that preferentially polarizes distal dendrites, 5-HT facilitated plateau potentials in 100% of the cells. Plateau potentials were also promoted by 5-HT focally applied on a dendrite by iontophoresis. Applied near the soma, 5-HT either promoted plateau potentials or inhibited spike generation. The latter effect was accompanied by a decrease in input resistance. Voltage-clamp recordings showed that the facilitation of plateau potentials mediated by L-type Ca(2+) channels was due to activation of 5-HT(2) receptors. These findings show that 5-HT regulates intrinsic properties of motoneurons in opposite ways: activation of 5-HT receptors in the soma region inhibits spike generation and plateau potentials, while activation of 5-HT(2) receptors in the dendrites and the soma region promotes spiking by facilitation of plateau potentials mediated by L-type Ca(2+) channels.
采用成年海龟脑片制备技术，通过细胞内记录法研究了5-羟色胺（5-HT）对脊髓运动神经元内在特性的影响。在所记录的细胞中，55%的细胞在细胞外培养基中加入5-HT后，通过细胞内电极施加去极化电流脉冲所引发的反应显示，5-HT促进了平台电位的产生。在其余45%的细胞中，5-HT具有抑制作用。然而，当用优先使远端树突极化的外加电场进行测试时，5-HT在100%的细胞中促进了平台电位的产生。通过离子电渗法将5-HT局部施加于树突上也能促进平台电位的产生。在胞体附近施加5-HT，要么促进平台电位的产生，要么抑制动作电位的产生。后一种效应伴随着输入电阻的降低。电压钳记录显示，由L型钙通道介导的平台电位的促进作用是由于5-HT2受体的激活。这些发现表明，5-HT以相反的方式调节运动神经元的内在特性：胞体区域5-HT受体的激活抑制动作电位的产生和平台电位，而树突和胞体区域5-HT2受体的激活通过促进由L型钙通道介导的平台电位来促进动作电位的产生。
