Manjarrez E, Rojas-Piloni J G, Jimenez I, Rudomin P
Department of Physiology, Biophysics and Neurosciences, Centro de Investigacion y Estudios Avanzados del Instituto Politecnico Nacional, Mexico DF.
J Physiol. 2000 Dec 1;529 Pt 2(Pt 2):445-60. doi: 10.1111/j.1469-7793.2000.00445.x.
We examined, in the anaesthetised cat, the influence of the neuronal ensembles producing spontaneous negative cord dorsum potentials (nCDPs) on segmental pathways mediating primary afferent depolarisation (PAD) of cutaneous and group I muscle afferents and on Ia monosynaptic activation of spinal motoneurones. The intraspinal distribution of the field potentials associated with the spontaneous nCDPs indicated that the neuronal ensembles involved in the generation of these potentials were located in the dorsal horn of lumbar segments, in the same region of termination of low-threshold cutaneous afferents. During the occurrence of spontaneous nCDPs, transmission from low-threshold cutaneous afferents to second order neurones in laminae III-VI, as well as transmission along pathways mediating PAD of cutaneous and Ib afferents, was facilitated. PAD of Ia afferents was instead inhibited. Monosynaptic reflexes of flexors and extensors were facilitated during the spontaneous nCDPs. The magnitude of the facilitation was proportional to the amplitude of the 'conditioning' spontaneous nCDPs. This led to a high positive correlation between amplitude fluctuations of spontaneous nCDPs and fluctuations of monosynaptic reflexes. Stimulation of low-threshold cutaneous afferents transiently reduced the probability of occurrence of spontaneous nCDPs as well as the fluctuations of monosynaptic reflexes. It is concluded that the spontaneous nCDPs were produced by the activation of a population of dorsal horn neurones that shared the same functional pathways and involved the same set of neurones as those responding monosynaptically to stimulation of large cutaneous afferents. The spontaneous activity of these neurones was probably the main cause of the fluctuations of the monosynaptic reflexes observed under anaesthesia and could provide a dynamic linkage between segmental sensory and motor pathways.
我们在麻醉猫身上研究了产生自发性脊髓背侧负电位（nCDPs）的神经元群对介导皮肤和I类肌肉传入纤维的初级传入去极化（PAD）的节段性通路以及对脊髓运动神经元Ia单突触激活的影响。与自发性nCDPs相关的场电位在脊髓内的分布表明，参与产生这些电位的神经元群位于腰段背角，即低阈值皮肤传入纤维的终止区域。在自发性nCDPs出现期间，从低阈值皮肤传入纤维到III - VI层二级神经元的传递以及沿介导皮肤和Ib传入纤维PAD的通路的传递都得到了促进。相反，Ia传入纤维的PAD受到抑制。在自发性nCDPs期间，屈肌和伸肌的单突触反射得到促进。促进的程度与“条件性”自发性nCDPs的幅度成正比。这导致自发性nCDPs的幅度波动与单突触反射的波动之间存在高度正相关。刺激低阈值皮肤传入纤维会短暂降低自发性nCDPs的发生概率以及单突触反射的波动。结论是，自发性nCDPs是由一群背角神经元的激活产生的，这些神经元共享相同的功能通路，并且与那些对大的皮肤传入纤维刺激产生单突触反应的神经元属于同一组。这些神经元的自发活动可能是麻醉下观察到的单突触反射波动的主要原因，并且可以在节段性感觉和运动通路之间提供动态联系。
