O'Leary Kathryn T, Loughlin Sandra E, Chen Yiling, Leslie Frances M
Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, California 92697, USA.
J Comp Neurol. 2008 Oct 20;510(6):655-72. doi: 10.1002/cne.21833.
Nicotinic acetylcholine receptors (nAChRs) mediate numerous visceral functions via medullary catecholamine (CA) neurons found in the nucleus tractus solitarius (NTS), dorsal motor nucleus of the vagus (DMV), and ventrolateral medulla (VLM). However, the nAChR subtypes involved are not known. We have therefore characterized expression of nine nAChR subunit mRNAs in adult and developing rat medullary CA nuclei using combined isotopic/nonisotopic in situ hybridization. Tyrosine hydroxylase (TH) mRNA, the CA-synthesizing enzyme, was used as a marker for CA neurons, because these nuclei consist of heterogeneous populations of cells. Subunit mRNA expression varied within and between nuclei, along the rostrocaudal axis, between cell types, and across development. All CA neurons expressed beta2 mRNA, whereas alpha2 mRNA was completely absent. alpha6 And beta3 mRNA expression were restricted mainly to the VLM. alpha4, alpha5, And alpha7 mRNA expression was significantly greater in the rostral than in the caudal VLM. alpha3 And beta4 mRNAs were highly expressed in the dorsal region of the NTS, whereas dense alpha7 mRNA expression was restricted to the DMV and ventral NTS. The remaining subunit mRNAs were detected to some degree in both DMV and NTS. Except for alpha4 mRNA, which peaked prenatally, expression levels of subunit transcripts in the NTS and DMV were lower during development compared with adults. In the VLM, alpha3, alpha4, and alpha5 mRNAs expression peaked perinatally, whereas alpha6 and beta3 levels increased with age. These variations in nAChR subunit mRNA expression suggest that different receptor subtypes may produce function-specific regulation of medullary CA systems.
烟碱型乙酰胆碱受体（nAChRs）通过孤束核（NTS）、迷走神经背运动核（DMV）和延髓腹外侧区（VLM）中的髓质儿茶酚胺（CA）神经元介导多种内脏功能。然而，所涉及的nAChR亚型尚不清楚。因此，我们使用同位素/非同位素原位杂交相结合的方法，对成年和发育中的大鼠髓质CA核中9种nAChR亚基mRNA的表达进行了表征。酪氨酸羟化酶（TH）mRNA作为CA合成酶，被用作CA神经元的标志物，因为这些核由异质性细胞群体组成。亚基mRNA的表达在核内和核间、沿头尾轴、细胞类型之间以及整个发育过程中均有所不同。所有CA神经元均表达β2 mRNA，而α2 mRNA则完全缺失。α6和β3 mRNA的表达主要局限于VLM。α4、α5和α7 mRNA在VLM头端的表达明显高于尾端。α3和β4 mRNA在NTS的背侧区域高表达，而密集的α7 mRNA表达则局限于DMV和NTS腹侧。其余亚基mRNA在DMV和NTS中均有一定程度的检测。除了在出生前达到峰值的α4 mRNA外，与成年期相比，NTS和DMV中亚基转录本的表达水平在发育过程中较低。在VLM中，α3、α4和α5 mRNA的表达在围产期达到峰值，而α6和β3的水平则随年龄增加。nAChR亚基mRNA表达的这些变化表明，不同的受体亚型可能对髓质CA系统产生功能特异性调节。
