Décossas Marion, Doudnikoff Evelyne, Bloch Bertrand, Bernard Véronique
Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5541, Laboratoire d'Histologie-Embryologie, Université Victor Ségalen-Bordeaux 2, 146 rue Léo-Saignat, 33076 Bordeaux Cedex, France.
Neurobiol Aging. 2005 Jul;26(7):1061-72. doi: 10.1016/j.neurobiolaging.2004.09.007. Epub 2004 Nov 23.
By using immunohistochemical approaches at the light and electron microscopic levels, we have shown that aging modifies the subcellular distribution of the m2 muscarinic autoreceptor (m2R) differentially at somato-dendritic postsynaptic sites and at axonal presynaptic sites in cholinergic basalocortical neurons, in vivo. In cholinergic perikarya and dendrites of the nucleus basalis magnocellularis (NBM), aging is associated with a decrease of the density of m2R at the plasma membrane and in the cytoplasm, suggesting a decrease of the total number of m2R in the somato-dendritic field. In contrast, the number of substance P receptors per somato-dendritic surface was not affected. In the frontal cortex (FC), we have shown a decrease of cytoplasmic m2R density also leading to a decrease of the number of m2R per surface of varicosities but with no change of the density of m2R at the membrane. Our results suggest that the decrease of m2R in the somato-dendritic field of the NBM, but not a modification of the number of presynaptic m2 autoreceptors at the plasma membrane in the FC, could contribute to the decrease of the efficacy of cholinergic transmission observed with aging in the rat.
通过在光学和电子显微镜水平上使用免疫组织化学方法，我们已经表明，在体内，衰老对胆碱能基底皮质神经元的体树突突触后位点和轴突突触前位点的M2毒蕈碱自身受体（m2R）的亚细胞分布有不同的影响。在大细胞基底核（NBM）的胆碱能胞体和树突中，衰老与质膜和细胞质中m2R密度的降低有关，这表明体树突区域中m2R的总数减少。相比之下，每个体树突表面的P物质受体数量没有受到影响。在额叶皮质（FC）中，我们已经表明细胞质m2R密度的降低也导致每个曲张体表面的m2R数量减少，但膜上m2R的密度没有变化。我们的结果表明，NBM体树突区域中m2R的减少，而不是FC中质膜上突触前m2自身受体数量的改变，可能导致在大鼠衰老过程中观察到的胆碱能传递效率的降低。
