Roth Adelheid L, Berg Darwin K
Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, USA.
J Comp Neurol. 2003 Oct 13;465(2):195-204. doi: 10.1002/cne.10856.
Nicotinic acetylcholine receptors containing the alpha7 gene product are widely expressed in the nervous system and have high calcium permeabilities that allow them to influence numerous calcium-dependent processes. Though often found at presynaptic locations, where they enhance transmitter release, the receptors can also occupy postsynaptic sites. Highest levels have been reported for chick ciliary ganglion neurons, where the postsynaptic receptors are concentrated on somatic spines arranged in clumps and appear as large receptor clusters. We show here that subpopulations of chick spinal cord neurons also express high levels of alpha7-containing receptors and arrange them in large clusters. The populations include peripheral motoneurons, presumptive preganglionic neurons, neurons adjacent to the lateral motor column, and possible interneurons in the ventral horn. In many cases, the receptor clusters codistribute with filamentous actin, as do clusters on ciliary ganglion neurons, where the actin represents a somatic spine constituent. In other respects, the spinal cord clusters differ. Those on motoneurons codistribute with the actin-associated component drebrin, as do the clusters on ciliary ganglion neurons, but the clusters on preganglionic neurons do not. Preganglionic neurons do, however, stain for lipid raft components as found for ciliary ganglion neurons, where the rafts embed the receptor-enriched spines. The results demonstrate that CNS neurons can configure alpha7-containing nicotinic receptors into large clusters but also suggest that the clusters are not likely to reflect a common molecular substructure on all neurons.
含有α7基因产物的烟碱型乙酰胆碱受体在神经系统中广泛表达，具有高钙通透性，使其能够影响众多钙依赖性过程。虽然这些受体常在突触前位置被发现，在那里它们可增强神经递质释放，但也可占据突触后位点。据报道，鸡睫状神经节神经元中的受体水平最高，其中突触后受体集中在成簇排列的体细胞棘上，并表现为大的受体簇。我们在此表明，鸡脊髓神经元亚群也表达高水平的含α7受体，并将它们排列成大簇。这些群体包括外周运动神经元、假定的节前神经元、外侧运动柱附近的神经元以及腹角中可能的中间神经元。在许多情况下，受体簇与丝状肌动蛋白共分布，睫状神经节神经元上的簇也是如此，其中肌动蛋白是体细胞棘的组成部分。在其他方面，脊髓簇有所不同。运动神经元上的簇与肌动蛋白相关成分drebrin共分布，睫状神经节神经元上的簇也是如此，但节前神经元上的簇则不然。然而，节前神经元确实像睫状神经节神经元那样对脂筏成分染色，在睫状神经节神经元中，脂筏嵌入富含受体的棘中。结果表明，中枢神经系统神经元可将含α7的烟碱型受体配置成大簇，但也表明这些簇不太可能反映所有神经元上的共同分子亚结构。
