Esser M J, Pronych S P, Allen G V
Dalhousie University, Faculty of Medicine, Department of Anatomy and Neurobiology, Halifax, Nova Scotia, Canada.
J Comp Neurol. 1998 Feb 22;391(4):526-44. doi: 10.1002/(sici)1096-9861(19980222)391:4<526::aid-cne8>3.0.co;2-2.
Cardiovascular regulatory neurons of the ventral medulla and pons are thought to have an important role in the mediation of trigeminal nociception-induced reflex cardiovascular responses. However, the neural pathways that link the spinal trigeminal nucleus with ventral medullary and pontine autonomic cell groups are poorly understood. The present study utilized injections of the highly sensitive anterograde tracer substance biotinylated dextran combined with immunocytochemistry for tyrosine hydroxylase, the synthesizing enzyme for catecholamines, to investigate the distribution and morphology of projections from the spinal trigeminal subnucleus caudalis to ventral medullary and pontine catecholaminergic cell groups. Injection of biotylinated dextran into the dorsal subnucleus caudalis produced dense anterograde labeling in dorsal regions of the medullary and pontine reticular formation including the dorsal medullary reticular field, the parvicellular reticular field, and the parvicellular reticular field pars anterior. In the ventral medullary and pontine reticular formation, light anterograde labeling tended to be distributed in close proximity to the distal dendrites of catecholaminergic neurons located in the C1, A1, and A5 regions. Injections of anterograde tracer into the dorsal medullary reticular field produced dense anterograde labeling in the ventral medullary and pontine reticular formation. Numerous terminal-like varicosities were observed in close proximity to catecholaminergic neurons located in the C1, A1, and A5 regions. These data suggest that trigeminal pain-induced reflex cardiovascular responses involve indirect projections that terminate in the dorsal medullary and pontine reticular formation before reaching ventral medullary and pontine catecholaminergic cell groups known to be involved in cardiovascular regulation.
延髓腹侧和脑桥的心血管调节神经元被认为在三叉神经伤害性感受诱导的反射性心血管反应的介导中起重要作用。然而，将脊髓三叉神经核与延髓腹侧和脑桥自主神经细胞群联系起来的神经通路却知之甚少。本研究利用注射高敏感性顺行示踪剂生物素化葡聚糖，并结合针对儿茶酚胺合成酶酪氨酸羟化酶的免疫细胞化学方法，来研究从三叉神经尾侧亚核到延髓腹侧和脑桥儿茶酚胺能细胞群的投射分布和形态。将生物素化葡聚糖注射到尾侧亚核背侧，在延髓和脑桥网状结构的背侧区域产生了密集的顺行标记，包括延髓背侧网状区、小细胞网状区和小细胞网状区前部。在延髓腹侧和脑桥网状结构中，轻度顺行标记倾向于分布在位于C1、A1和A5区域的儿茶酚胺能神经元的远端树突附近。将顺行示踪剂注射到延髓背侧网状区，在延髓腹侧和脑桥网状结构中产生了密集的顺行标记。在位于C1、A1和A5区域的儿茶酚胺能神经元附近观察到许多终末样膨体。这些数据表明，三叉神经痛诱导的反射性心血管反应涉及间接投射，这些投射在到达已知参与心血管调节的延髓腹侧和脑桥儿茶酚胺能细胞群之前，先终止于延髓背侧和脑桥网状结构。
