Kamogawa H, Hiraba H, Manabe K, Sakanashi T, Sekiguchi T, Inage T
Department of Physiology, Nihon University School of Dentistry, Kanda-surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
Brain Res. 1998 Feb 23;785(1):18-23. doi: 10.1016/s0006-8993(97)01372-3.
Intracellular injection of horseradish peroxidase (HRP) into 58 masseteric motoneurons identified by antidromic activation was performed in cats under pentobarbital anesthesia. Monosynaptic EPSPs were evoked by masseteric nerve stimuli in 52 cells, and were absent in the remaining six cells. The antidromic nature of the evoked spikes was confirmed by IS-SD separation observed at high frequency (50 Hz) stimulation. Motoneurons with monosynaptic excitation from masseter afferents showed IPSPs following stimulation of lingual and inferior alveolar nerves. Motoneurons which did not show monosynaptic excitation from masseter afferents showed no IPSPs from the above nerves. There were no differences in cell size or the number of stem dendrites between motoneurons with and without monosynaptic EPSPs. No recurrent collaterals were observed in any motor axons. Motoneurons with monosynaptic EPSPs were located at all rostrocaudal levels throughout the trigeminal motor nucleus, whereas motoneurons without such EPSPs were encountered only at the middle level. Dendrites of motoneurons with monosynaptic EPSPs did not extend into the medial portion of the nucleus where motoneurons innervating the anterior belly of the digastric muscle were located. In contrast, motoneurons without monosynaptic EPSPs had dendrite branches extending well into the medial part. The results show that there are two subpopulations of masseteric motoneurons that differ in peripheral inputs as well as dendritic morphology.
在戊巴比妥麻醉下的猫中，向58个通过逆向激活鉴定的咬肌运动神经元内注射辣根过氧化物酶（HRP）。52个细胞通过咬肌神经刺激诱发了单突触兴奋性突触后电位（EPSP），其余6个细胞未出现。在高频（50Hz）刺激下观察到的逆向冲动与正向冲动的分离证实了诱发动作电位的逆向性质。来自咬肌传入纤维具有单突触兴奋的运动神经元在刺激舌神经和下牙槽神经后出现抑制性突触后电位（IPSP）。未显示来自咬肌传入纤维单突触兴奋的运动神经元在上述神经刺激后未出现IPSP。有和没有单突触EPSP的运动神经元在细胞大小或树突干数量上没有差异。在任何运动轴突中均未观察到回返侧支。具有单突触EPSP的运动神经元位于整个三叉神经运动核的所有 rostrocaudal 水平，而没有这种 EPSP 的运动神经元仅在中间水平出现。具有单突触EPSP的运动神经元的树突不延伸到支配二腹肌前腹的运动神经元所在的核的内侧部分。相反，没有单突触EPSP的运动神经元的树突分支很好地延伸到内侧部分。结果表明，咬肌运动神经元有两个亚群，它们在外周输入以及树突形态上存在差异。
