Luo P, Dessem D
Department of Physiology, University of Maryland Dental School, Baltimore, Maryland 21201-1586, USA.
J Comp Neurol. 1999 Apr 12;406(3):384-401. doi: 10.1002/(sici)1096-9861(19990412)406:3<384::aid-cne7>3.0.co;2-7.
Neuronal microcircuits involving jaw-muscle spindle afferents and jaw-elevator motoneurons were studied via retrograde and intracellular labeling in rats. Initially, trigeminal motoneurons were retrogradely labeled from horseradish peroxidase (HRP) injections into the temporalis and masseter muscles. The intracellular response of jaw-muscle spindle afferent neurons was then characterized during palpation, ramp and hold, and sinusoidal stretching of the jaw-closing muscles. Biotinamide was injected into these neurons, and the tissue was processed for the visualization of HRP and biotinamide. The ultrastructure of 243 intracellularly stained jaw-muscle spindle afferent boutons located within the trigeminal motor nucleus (Vmo) was examined. Eighty-five of these boutons synapsed with motoneurons retrogradely labeled with HRP, and 158 boutons synapsed with unlabeled structures within the Vmo. All spindle afferent boutons contained clear, spherical synaptic vesicles. Although the majority of boutons were S type, a few labeled jaw-muscle spindle afferent boutons possessed a long, narrow cleft, with a subsynaptic cistern comparable to previous descriptions of C-type boutons. Sixty-eight percent of spindle afferent boutons synapsed with large or medium-sized, retrogradely labeled motoneuron dendrites, and 32% synapsed with retrogradely labeled somata. In numerous instances, spindle afferent boutons synapsed with trigeminal motoneuron dendritic or somatic spines. Most of the synapses between spindle afferent boutons and trigeminal motoneuron dendrites were asymmetric, and the greatest percentage of axosomatic synapses between spindle afferents and trigeminal motoneurons were symmetric. Approximately 24% of spindle afferent boutons constituted the intermediate element of a axoaxodendritic or axoaxosomatic assemblage, implying that some jaw-muscle spindle afferent synapses with trigeminal motoneurons are presynaptically modulated.
通过对大鼠进行逆行标记和细胞内标记，研究了涉及颌肌梭传入神经和颌上提运动神经元的神经元微回路。最初，将辣根过氧化物酶（HRP）注射到颞肌和咬肌中，对三叉神经运动神经元进行逆行标记。然后，在触诊、斜坡和保持以及下颌闭合肌的正弦拉伸过程中，对颌肌梭传入神经元的细胞内反应进行了表征。将生物素酰胺注射到这些神经元中，并对组织进行处理以可视化HRP和生物素酰胺。检查了位于三叉神经运动核（Vmo）内的243个细胞内染色的颌肌梭传入终扣的超微结构。其中85个终扣与用HRP逆行标记的运动神经元形成突触，158个终扣与Vmo内未标记的结构形成突触。所有梭传入终扣都含有清晰的球形突触小泡。虽然大多数终扣是S型，但一些标记的颌肌梭传入终扣有一个长而窄的裂隙，有一个突触下池，类似于先前对C型终扣的描述。68%的梭传入终扣与大或中型、逆行标记的运动神经元树突形成突触，32%与逆行标记的胞体形成突触。在许多情况下，梭传入终扣与三叉神经运动神经元的树突棘或体细胞棘形成突触。梭传入终扣与三叉神经运动神经元树突之间的大多数突触是不对称的，梭传入与三叉神经运动神经元之间的轴体突触中最大比例是对称的。大约24%的梭传入终扣构成轴突-轴突-树突或轴突-轴突-体细胞组合的中间元件，这意味着一些颌肌梭传入与三叉神经运动神经元的突触受到突触前调节。
