Tucker D C, Saper C B, Ruggiero D A, Reis D J
J Comp Neurol. 1987 May 22;259(4):591-603. doi: 10.1002/cne.902590408.
We studied the organization of projections from the C1 adrenergic and A1 noradrenergic cell groups in the ventrolateral medulla (VLM) to the hypothalamus and the spinal cord by using a combination of retrograde transport of fluorescent tracers and immunocytochemistry. Three issues were addressed. Neurons in the VLM that stain immunohistochemically for phenylethanolamine N-methyltransferase (PNMT) have been assumed to be adrenergic. However, the presence of PNMT-immunoreactive neurons in the hypothalamus that do not stain for tyrosine hydroxylase (TH) prompted us to re-evaluate the VLM by an elution-restaining immunohistochemical procedure. We confirmed that nearly all of the rostral medullary PNMT-immunoreactive neurons also stained for TH. By contrast, in the caudal medulla, very few TH-positive neurons stained for PNMT. Neurons of the C1 group in the rostral VLM project both to the thoracic spinal cord and to the hypothalamus. To determine whether individual C1 neurons send collaterals to the hypothalamus and spinal cord, we injected different-colored fluorescent dyes (diamidino yellow or fast blue) into the thoracic spinal gray matter and either the median preoptic (MnPO) or paraventricular (PVH) nuclei of the hypothalamus. Very few double-labeled neurons were found in the VLM, indicating that hypothalamic and spinal cord projections arise from almost completely independent populations of cells. Approximately half of the neurons projecting to the spinal cord from rostral VLM were not immunoreactive for TH or PNMT, indicating that a substantial part of this projection is noncatecholaminergic. The MnPO and the PVH both receive extensive catecholaminergic inputs from the VLM. We also used fluorescent retrograde tracers to determine whether individual VLM neurons send collaterals to both hypothalamic sites. Approximately 20% of neurons projecting to the MnPO in the rostral two thirds of the VLM also sent collaterials to the PVH, nearly all of these neurons being TH-positive. The collateralization of the VLM catecholaminergic projection to the hypothalamus may provide an anatomical substrate for integration of fore-brain participation in cardiovascular regulation. In contrast, the adrenergic projection from the VLM to the intermediolateral column of the spinal cord arises from a separate population of neurons.
我们通过结合荧光示踪剂的逆行运输和免疫细胞化学方法，研究了延髓腹外侧区（VLM）中C1肾上腺素能和A1去甲肾上腺素能细胞群向下丘脑和脊髓的投射组织。我们探讨了三个问题。免疫组织化学染色显示苯乙醇胺N-甲基转移酶（PNMT）的VLM中的神经元被认为是肾上腺素能的。然而，下丘脑中存在不表达酪氨酸羟化酶（TH）的PNMT免疫反应性神经元，这促使我们通过洗脱-复染免疫组织化学程序重新评估VLM。我们证实，几乎所有延髓头端的PNMT免疫反应性神经元也表达TH。相比之下，在延髓尾端，很少有TH阳性神经元表达PNMT。延髓头端VLM中的C1组神经元既投射到胸段脊髓，也投射到下丘脑。为了确定单个C1神经元是否向下丘脑和脊髓发出侧支，我们将不同颜色的荧光染料（双脒基黄或固蓝）注入胸段脊髓灰质以及下丘脑的正中视前核（MnPO）或室旁核（PVH）。在VLM中发现的双标记神经元很少，这表明下丘脑和脊髓的投射几乎完全来自独立的细胞群。从延髓头端VLM投射到脊髓的神经元中，约有一半对TH或PNMT无免疫反应，这表明该投射的很大一部分是非儿茶酚胺能的。MnPO和PVH都接受来自VLM的广泛的儿茶酚胺能输入。我们还使用荧光逆行示踪剂来确定单个VLM神经元是否向下丘脑的两个部位发出侧支。在VLM头端三分之二区域投射到MnPO的神经元中，约20%也向PVH发出侧支，几乎所有这些神经元都是TH阳性的。VLM向下丘脑的儿茶酚胺能投射的侧支化可能为前脑参与心血管调节的整合提供了解剖学基础。相比之下，VLM向脊髓中间外侧柱的肾上腺素能投射来自另一群神经元。
