Woulfe J M, Flumerfelt B A, Hrycyshyn A W
Department of Anatomy, University of Western Ontario, London, Canada.
Exp Neurol. 1990 Sep;109(3):308-22. doi: 10.1016/s0014-4886(05)80022-6.
Immunohistochemical localization of the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT) was employed to reveal the anatomical organization of the A1 noradrenergic cell group in the caudal ventrolateral medulla oblongata of the rat. Subsequently, the supraspinal efferent axonal projections of A1 were investigated with a view to elucidating the anatomical substrates underlying its postulated function in central fluid and cardiovascular homeostasis. Within the caudal medulla, DBH-positive/PNMT-negative (noradrenergic) neurons were observed extending bilaterally through the ventrolateral medullary reticular formation from upper cervical spinal cord levels to the level of the area postrema. At the rostral pole of A1, its neurons intermingled with PNMT-immunoreactive perikarya of the more rostrally situated C1 adrenergic cell group. Discrete injections of the anterogradely transported plant lectin Phaseolus vulgaris leucoagglutinin (PHA-L) into A1 resulted in terminal labeling in a number of presumptive efferent target sites including the nucleus of the solitary tract, rostral ventrolateral medulla, dorsal parabrachial nucleus, Kolliker-Fuse nucleus, central grey, dorsomedial nucleus of the hypothalamus, perifornical region, zona incerta, lateral hypothalamus, paraventricular nucleus of the hypothalamus, supraoptic nucleus, bed nucleus of the stria terminalis, and organum vasculosum of the lamina terminalis. Tissue sections adjacent to those reacted for PHA-L were processed immunohistochemically for DBH to determine if anterogradely labeled terminals were localized in regions that demonstrated appropriate immunoreactivity. The majority of regions in which PHA-L terminal labeling was present also exhibited moderate to intense DBH activity. These experiments provide neuroanatomical evidence for direct efferent pathways from the A1 noradrenergic cell group to a number of supraspinal sites that have been reliably implicated in the neural circuitry underlying the central regulation of fluid and cardiovascular homeostasis. Furthermore, the results suggest a selective anatomical interrelation between A1 and sites in the basal forebrain and hypothalamus in which vasopressinergic neurons have been previously demonstrated. It is postulated that the noradrenergic A1 projections observed in this investigation represent the morphological substrate through which A1 exerts a significant influence on cardiovascular regulatory mechanisms.
采用免疫组织化学方法定位儿茶酚胺生物合成酶酪氨酸羟化酶（TH）、多巴胺β-羟化酶（DBH）和苯乙醇胺N-甲基转移酶（PNMT），以揭示大鼠延髓尾侧腹外侧A1去甲肾上腺素能细胞群的解剖结构。随后，研究了A1的脊髓上发出的轴突投射，以阐明其在中枢液体和心血管稳态中假定功能的解剖学基础。在延髓尾部，观察到DBH阳性/PNMT阴性（去甲肾上腺素能）神经元双侧延伸，穿过延髓腹外侧网状结构，从上颈脊髓水平到最后区水平。在A1的头端极，其神经元与位于更靠前的C1肾上腺素能细胞群的PNMT免疫反应性核周体混合。将顺行运输的植物凝集素菜豆白细胞凝集素（PHA-L）离散注射到A1中，导致在许多假定的传出靶位点出现终末标记，包括孤束核、延髓头端腹外侧、臂旁背核、 Kölliker-Fuse核、中央灰质、下丘脑背内侧核、穹窿周区、未定带、下丘脑外侧、下丘脑室旁核、视上核、终纹床核和终板血管器。对与PHA-L反应的组织切片相邻的组织切片进行DBH免疫组织化学处理，以确定顺行标记的终末是否位于显示适当免疫反应性的区域。存在PHA-L终末标记的大多数区域也表现出中度至强烈的DBH活性。这些实验提供了神经解剖学证据，证明从A1去甲肾上腺素能细胞群到一些脊髓上部位存在直接传出通路，这些部位已被可靠地牵涉到中枢调节液体和心血管稳态的神经回路中。此外，结果表明A1与基底前脑和下丘脑部位之间存在选择性解剖学相互关系，在这些部位先前已证明有加压素能神经元。据推测，本研究中观察到的去甲肾上腺素能A1投射代表了A1对心血管调节机制产生重大影响的形态学基础。
