Department of Physiology, University of Bern, Bern, Switzerland.
J Neurophysiol. 2009 Oct;102(4):2441-52. doi: 10.1152/jn.00244.2009. Epub 2009 Aug 12.
The vertebrate spinal cord is equipped with a number of neuronal networks that underlie repetitive patterns of behavior as locomotion. Activity in such networks is mediated not only by intrinsic cellular properties but also by synaptic coupling. In this study, we focused on the modulation of the intrinsic activity by 5-hydroxytryptamine (5-HT, serotonin) and the cholinergic agonist muscarine in spinal cord cultures (embryonic age 14 rats). We investigated theses cultures (slices and dissociated cells) at the network level using multielectrode arrays (MEAs) and at the cellular level using whole cell patch clamp. All cultures showed bursting network activity and intrinsic activity when gamma-aminobutyric acid, glycine, and glutamate transmission was blocked. Using MEAs, we observed an increase of the intrinsic activity in the ventral part of the slices with 5-HT and muscarine. In single-cell recordings we found that 43 and 35% of the cells that were silent in the absence of fast synaptic activity were transformed into intrinsically spiking cells by 5-HT and muscarine, respectively. We tested the hypothesis that these neuromodulators act via modulation of the persistent sodium currents (I(NaP)) in these neurons. We found that 5-HT increased threefold the amplitude of I(NaP), specifically in the nonintrinsically spiking cells, and thus switched these cells into intrinsically spiking cells via activation of 5-HT(2) receptor and the phospholipase C pathway. In contrast, the effect of muscarine on nonintrinsically spiking neurons seems to be independent of I(NaP). We conclude from these findings that serotoninergic and cholinergic modulation can turn silent into spontaneously spiking neurons and thus initiate new sources of activity for rhythm generation in spinal networks.
脊椎动物脊髓配备了许多神经元网络，这些网络是运动等重复行为模式的基础。这些网络中的活动不仅受内在细胞特性的调节，还受突触耦联的调节。在这项研究中，我们专注于 5-羟色胺（5-HT，血清素）和胆碱能激动剂毒蕈碱在脊髓培养物（胚胎 14 天大的大鼠）中对内在活动的调制。我们使用多电极阵列（MEA）在网络水平和全细胞膜片钳在细胞水平研究了这些培养物（切片和分离细胞）。当阻断 γ-氨基丁酸、甘氨酸和谷氨酸传递时，所有培养物都显示出爆发性网络活动和内在活动。使用 MEA，我们观察到 5-HT 和毒蕈碱增加了切片腹侧部分的内在活动。在单细胞记录中，我们发现 43%和 35%的在没有快速突触活动的情况下处于沉默状态的细胞分别被 5-HT 和毒蕈碱转化为内在放电细胞。我们检验了这些神经调质通过调节这些神经元中的持续钠电流（I(NaP)）起作用的假设。我们发现 5-HT 将 I(NaP)的幅度增加了三倍，特别是在非内在放电细胞中，并且通过激活 5-HT(2)受体和磷脂酶 C 途径将这些细胞转换为内在放电细胞。相比之下，毒蕈碱对非内在放电神经元的作用似乎独立于 I(NaP)。从这些发现中我们得出结论，5-羟色胺能和胆碱能调制可以将沉默细胞转变为自发放电细胞，从而为脊髓网络中的节律产生引发新的活动源。
