Whitehead M C
J Comp Neurol. 1986 Feb 1;244(1):72-85. doi: 10.1002/cne.902440106.
The solitary nucleus is the first level of the central nervous system where processing of taste information can occur. A structural basis for that processing was investigated. Facial taste afferent axons were labelled by application of horseradish peroxidase to either the chorda tympani or the geniculate ganglion. The labelled afferent fibers in the rostral solitary nucleus were studied with light and electron microscopy. Preterminal facial taste afferent axons enter the nucleus from the solitary tract with a pronounced lateral to medial trajectory. The axons bear numerous preterminal and terminal swellings that, with the electron microscope, were identified as synaptic endings located in glomeruli. The endings are ovoid or scalloped, indented by structures that surround them. The primary afferent endings contain large, round vesicles and synapse, by means of slightly asymmetrical junctional complexes, on small dendrites and spines. Two types of unlabelled endings, surrounding the labelled ones, contact the dendrites receiving taste afferent input or contact the endings of taste afferent axons themselves. One type is variable in size and contains scattered large round vesicles. It resembles a presynaptic dendrite. The other is a small axonal ending packed with small, pleomorphic vesicles, that engages in symmetrical junctions. The synaptic milieu of the taste endings allows for the possibility of modulation of taste-elicited activity in afferent endings or second-order neurons by other, possibly interneuronal, inputs.
孤束核是中枢神经系统中味觉信息处理可能发生的第一级结构。对该处理过程的结构基础进行了研究。通过将辣根过氧化物酶应用于鼓索或膝状神经节来标记面神经味觉传入轴突。用光学显微镜和电子显微镜研究了延髓孤束核中标记的传入纤维。终末前的面神经味觉传入轴突以明显的从外侧到内侧的轨迹从孤束进入该核。轴突带有许多终末前和终末膨体，在电子显微镜下，这些膨体被鉴定为位于小球体内的突触终末。这些终末呈卵圆形或扇形，被周围的结构压出凹陷。初级传入终末含有大的圆形囊泡，并通过稍不对称的连接复合体与小的树突和棘突触。两种未标记的终末围绕着标记的终末，与接受味觉传入输入的树突接触或与味觉传入轴突的终末本身接触。一种类型大小不一，含有散在的大圆形囊泡。它类似于突触前树突。另一种是小的轴突终末，充满了小的、多形性囊泡，形成对称连接。味觉终末的突触环境使得其他可能是中间神经元的输入有可能调节传入终末或二级神经元中由味觉引发的活动。
