Kiyohara S, Yamashita S, Lamb C F, Finger T E
Department of Chemistry and BioScience, Faculty of Science, Kagoshima University, Japan.
Brain Res. 1999 Sep 11;841(1-2):93-100. doi: 10.1016/s0006-8993(99)01785-0.
Previous studies in several fishes including catfish, have shown that primary trigeminal nerve (NV) axons terminate not only in the principal and spinal trigeminal nuclei, but in the facial (gustatory) lobes. The present study was undertaken to determine the extent and distribution of trigeminal terminations within the facial lobe (FL) and principal trigeminal nucleus (nVpr) in the channel catfish, Ictalurus punctatus. In order to reveal the distribution of trigeminal fibers, the carbocyanine dye, diI, was applied to the central cut stump of the trigeminal root in isolated, paraformaldehyde-fixed brains. After a diffusion period of 10-90 days, the brains were serially sectioned on a vibratome and examined with epifluorescence. The trigeminal motor nucleus (nVm) and principal sensory nucleus lie near the level of entrance of NV. The majority of primary trigeminal fibers, however, sweep caudally after entering into the brain to form the descending root. At the level of the caudal third of the FL, collaterals emitted by the descending root fibers turn medially and dorsally to terminate in the FL. The trigeminal fibers are coarser than the facial nerve (NVII) fibers which terminate within the same structure. The trigeminal fibers terminate throughout the FL except for the lateral-most lobule which contains the representation of taste buds innervated by the recurrent branch of NVII, i.e., those over the trunk and tail of the animal. These results show that in catfish, the trigeminal input to the primary gustatory complex is restricted to those portions of the nucleus receiving chemosensory inputs from the face and barbels, i.e., the trigeminally innervated sensory fields.
此前对包括鲶鱼在内的几种鱼类的研究表明，三叉神经（NV）的初级轴突不仅终止于三叉神经主核和脊髓核，还终止于面神经（味觉）叶。本研究旨在确定斑点叉尾鮰三叉神经在面神经叶（FL）和三叉神经主核（nVpr）内的终止范围和分布情况。为了揭示三叉神经纤维的分布，将羰花青染料diI应用于分离的、经多聚甲醛固定的大脑中三叉神经根的中央切断端。经过10 - 90天的扩散期后，在振动切片机上对大脑进行连续切片，并用落射荧光显微镜进行检查。三叉神经运动核（nVm）和主要感觉核位于NV进入的水平附近。然而，大多数三叉神经初级纤维在进入大脑后向尾侧延伸，形成下行根。在FL尾侧三分之一的水平，下行根纤维发出的侧支转向内侧和背侧，终止于FL。三叉神经纤维比终止于同一结构内的面神经（NVII）纤维更粗。除了最外侧的小叶外，三叉神经纤维终止于整个FL，最外侧的小叶包含由NVII的返支支配的味蕾，即动物躯干和尾部的味蕾。这些结果表明，在鲶鱼中，三叉神经向初级味觉复合体的输入仅限于该核中接受来自面部和触须化学感觉输入的部分，即三叉神经支配的感觉区域。
