Kawa K, Roper S
J Physiol. 1984 Jan;346:301-20. doi: 10.1113/jphysiol.1984.sp015023.
Parasympathetic neurones in the submandibular ganglion of the rat innervate the submandibular and sublingual salivary glands. Neurones which innervate the submandibular gland (s.m. neurones) are usually located along the salivary ducts which drain both glands. Neurones which innervate the sublingual gland (s.l. neurones) are located in the thin sheet of tissue which lies between the salivary ducts and the lingual nerve. The existence and characteristics of intrinsic synaptic connexions were studied electrophysiologically in these two divisions of the submandibular ganglion. Three days or more after denervating the ganglion two types of excitatory intrinsic synaptic potentials--chemical and electrical--were recorded in ganglion cells. Chemical synaptic responses were reversibly blocked by nicotinic antagonists such as hexamethonium (10 microM) and D-tubocurarine (100 microM). Intrinsic chemical synapses were common among s.m. neurones (present in 72% of neurones) but only 12% of s.l. neurones were coupled with chemical synapses. Electrical coupling was found among 31% of s.m. neurones but was not observed between s.l. neurones. Electrotonic coupling in s.m. neurones in denervated and intact ganglia was directly demonstrated by impaling adjacent neurones with separate micro-electrodes. The average coupling ratio for current pulses injected into one cell and recorded in the adjacent cell was 0.06. During the first 30 days after birth, the number of synaptic inputs from preganglionic (chorda tympani) axons was markedly reduced in both s.m. and s.l. neurones, whereas the incidence of electrical synaptic connexions remained unchanged. The effect of long-term denervation (up to 4 months) on intrinsic synapses was examined. The membrane properties of the parasympathetic neurones and the intrinsic synaptic connexions were maintained without marked changes. It is concluded that the submandibular ganglion in the rat consists of two distinct populations of parasympathetic neurones. The two classes of neurones differ in (1) their location within the ganglion, (2) their target organs and (3) the incidence of intrinsic synapses. Possible mechanisms for the development, maintenance and function of these intrinsic synapses are discussed.
大鼠下颌下神经节中的副交感神经元支配下颌下腺和舌下腺。支配下颌下腺的神经元（下颌下神经元）通常沿着引流这两个腺体的唾液导管分布。支配舌下腺的神经元（舌下神经元）位于唾液导管和舌神经之间的薄组织片中。用电生理学方法研究了下颌下神经节这两个部分中内在突触连接的存在和特征。在神经节去神经支配三天或更长时间后，在神经节细胞中记录到两种类型的兴奋性内在突触电位——化学性和电性。化学性突触反应可被烟碱拮抗剂如六甲铵（10微摩尔）和筒箭毒碱（100微摩尔）可逆性阻断。内在化学性突触在下颌下神经元中很常见（72%的神经元中存在），但只有12%的舌下神经元与化学性突触相连。在31%的下颌下神经元中发现了电耦合，但在舌下神经元之间未观察到。通过用单独的微电极刺入相邻神经元，直接证明了去神经支配和完整神经节中下颌下神经元的电紧张耦合。注入一个细胞并在相邻细胞中记录的电流脉冲的平均耦合比为0.06。在出生后的前30天内，下颌下和舌下神经元中来自节前（鼓索）轴突的突触输入数量明显减少，而电突触连接的发生率保持不变。研究了长期去神经支配（长达4个月）对内在突触的影响。副交感神经元的膜特性和内在突触连接得以维持，没有明显变化。结论是，大鼠下颌下神经节由两个不同的副交感神经元群体组成。这两类神经元在以下方面存在差异：（1）它们在神经节内的位置，（2）它们的靶器官，以及（3）内在突触的发生率。讨论了这些内在突触的发育、维持和功能的可能机制。
