Athanassiadis T, Westberg K-G, Olsson K A, Kolta A
Department of Integrative Medical Biology, Section for Physiology, Umeå University, SE-901 87 Umeå, Sweden.
Eur J Neurosci. 2005 Dec;22(12):3099-110. doi: 10.1111/j.1460-9568.2005.04479.x.
A population of neurons in the trigeminal principal sensory nucleus (NVsnpr) fire rhythmically during fictive mastication induced in the in vivo rabbit. To elucidate whether these neurons form part of the central pattern generator (CPG) for mastication, we performed intracellular recordings in brainstem slices taken from young rats. Two cell types were defined, nonbursting (63%) and bursting (37%). In response to membrane depolarization, bursting cells, which dominated in the dorsal part of the NVsnpr, fired an initial burst followed by single spikes or recurring bursts. Non-bursting neurons, scattered throughout the nucleus, fired single action potentials. Microstimulation applied to the trigeminal motor nucleus (NVmt), the reticular border zone surrounding the NVmt, the parvocellular reticular formation or the nucleus reticularis pontis caudalis (NPontc) elicited a postsynaptic potential in 81% of the neurons tested for synaptic inputs. Responses obtained were predominately excitatory and sensitive to glutamatergic antagonists DNQX and/or APV. Some inhibitory and biphasic responses were also evoked. Bicuculline methiodide or strychnine blocked the IPSPs indicating that they were mediated by GABA(A) or glycinergic receptors. About one-third of the stimulations activated both types of neurons antidromically, mostly from the masseteric motoneuron pool of NVmt and dorsal part of NPontc. In conclusion, our new findings show that some neurons in the dorsal NVsnpr display both firing properties and axonal connections which support the hypothesis that they may participate in masticatory pattern generation. Thus, the present data provide an extended basis for further studies on the organization of the masticatory CPG network.
在体内兔诱发的假咀嚼过程中,三叉神经主感觉核(NVsnpr)中的一群神经元有节律地放电。为了阐明这些神经元是否构成咀嚼中枢模式发生器(CPG)的一部分,我们在取自幼鼠的脑干切片中进行了细胞内记录。定义了两种细胞类型,非爆发性(63%)和爆发性(37%)。在膜去极化时,在NVsnpr背侧占主导的爆发性细胞先发放一个初始爆发,随后是单个动作电位或反复爆发。非爆发性神经元散布于整个核内,发放单个动作电位。对三叉神经运动核(NVmt)、围绕NVmt的网状边界区、小细胞网状结构或脑桥尾侧网状核(NPontc)施加微刺激,在81%接受突触输入测试的神经元中诱发了突触后电位。获得的反应主要是兴奋性的,并且对谷氨酸能拮抗剂DNQX和/或APV敏感。也诱发了一些抑制性和双相反应。甲基东莨菪碱或士的宁阻断了抑制性突触后电位(IPSPs),表明它们是由GABA(A)或甘氨酸能受体介导的。大约三分之一的刺激以逆向方式激活了两种类型的神经元,主要来自NVmt的咬肌运动神经元池和NPontc的背侧部分。总之,我们的新发现表明,NVsnpr背侧的一些神经元表现出放电特性和轴突连接,支持了它们可能参与咀嚼模式生成的假说。因此,目前的数据为进一步研究咀嚼CPG网络的组织提供了扩展的基础。