Preproenkephalin mRNA is expressed by C1 and non-C1 barosensitive bulbospinal neurons in the rostral ventrolateral medulla of the rat
Preproenkephalin mRNA is expressed by C1 and non-C1 barosensitive bulbospinal neurons in the rostral ventrolateral medulla of the rat
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DOI：
10.1002/cne.1196
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发表时间：
2001-06-18
影响因子：
2.5
通讯作者：
Guyenet, PG
中科院分区：
文献类型：
--
作者：
Stornetta, RL;Schreihofer, AM;Guyenet, PG
胸腰段脊髓的自主神经区接受来自棘上来源的密集脑啡肽(ENK)神经支配，包括头端延髓腹外侧区(RVLM)。在本研究中，我们试图确定RVLM的压力敏感球脊髓(BSBS)神经元是否表达前脑啡肽原(PPE)mRNA。将荧光金(FG)注入上胸段脊髓后，PPE阳性神经元(PPE+神经元)在延髓腹外侧部被逆行标记。在RVLM的最顶端，29%的球脊髓PPE+细胞为酪氨酸羟基酶免疫阳性细胞(TH-ir)，后者占球脊髓TH-ir细胞的19.4%。我们通过两种方法确定了延髓PPE+RVLM神经元是否具有压力敏感性。首先，我们检测了清醒大鼠在肼类药物诱导的降压(73+/-2 mm Hg)2小时后，FG标记的RVLM神经元产生Fos的情况。肼丙嗪(10 mg/kg静脉注射)在所检查的延髓腹外侧部的所有水平上，Fos-ir神经元的数量增加了2-8倍。在RVLM，54%的球脊髓PPE阳性神经元为Fos-ir，而这种细胞在延髓腹外侧尾部较少见。其次，我们在麻醉大鼠细胞外记录单个BSBS RVLM单位，并在细胞旁填充生物素胺。充满生物胺的神经元多为PPE+(10/17)，PPE+BSBS细胞的轴突传导速度较不含PPE的细胞快(4.2vs.0.67m/s)。10个PPE+BSBS RVLM神经元中有4个为TH阳性神经元。综上所述，PPE mRNA主要由RVLM BSBS神经元和轻度有髓脊髓轴突表达。PPE mRNA存在于大多数非儿茶酚胺能BSBS神经元中，也存在于约20%的延髓C1神经元中。BSBS RVLM神经元很可能为交感节前神经元提供了主要的ENK输入，PPE mRNA是第一个被发现的非C1型BSBS RVLM神经元的阳性表型。(C)2001年Wiley-Liss，Inc.
The autonomic regions of the thoracolumbar spinal cord receive a dense enkephalinergic (ENK) innervation from supraspinal sources, including the rostral ventrolateral medulla (RVLM). In the present study, we sought to determine whether the barosensitive bulbospinal (BSBS) neurons of the RVLM express preproenkephalin (PPE) mRNA. After injection of Fluoro-Gold (FG) into the upper thoracic spinal cord, neurons with PPE mRNA (PPE+ neurons) were retrogradely labeled throughout the ventrolateral medulla. At the most rostral RVLM level, 29% of bulbospinal PPE + cells were tyrosine hydroxylase-immunore active (TH-ir) and the latter constituted 19.4% of the bulbospinal TH-ir cells. We determined whether the bulbospinal PPE+ RVLM neurons are barosensitive in two ways. First, we examined Fos production by FG-labeled RVLM neurons after 2 hours of hydralazine-induced hypotension (to 73 +/- 2 mm Hg) in conscious rats. Hydralazine (10 mg/kg i.v.) increased the number of Fos-ir neurons by two- to eightfold at all levels of the ventrolateral medulla examined. In the RVLM, 54% of bulbospinal PPE+ neurons were Fos-ir, whereas such cells were more rarely found at caudal ventrolateral medullary levels. Second, we recorded individual BSBS RVLM units extracellularly in anesthetized rats and filled them juxtacellularly with biotinamide. Most biotinamide-filled neurons were PPE+ (10 of 17), and the PPE+ BSBS cells had a faster axonal conduction velocity than those without PPE mRNA (4.2 vs. 0.67 m/sec). Four of the 10 PPE+ BSBS RVLM neurons were TH-ir. In summary, PPE mRNA is predominantly expressed by RVLM BSBS neurons with lightly myelinated spinal axons. PPE mRNA is present in most noncatecholaminergic BSBS neurons and also in approximately 20% of the bulbospinal C1 neurons. BSBS RVLM neurons most likely provide a major ENK input to sympathetic preganglionic neurons and PPE mRNA is the first identified positive phenotype of the non-C1 BSBS RVLM neurons. (C) 2001 Wiley-Liss, Inc.