Kruger L, Bendotti C, Rivolta R, Samanin R
Department of Anatomy and Cell Biology, UCLA Medical Center 90024.
J Comp Neurol. 1993 Jul 15;333(3):417-34. doi: 10.1002/cne.903330308.
Regional distribution of gene expression of the axonal growth-associated protein, GAP-43, was studied in adult rat brains by in situ hybridization autoradiography to determine the features of mature neuronal populations that synthesize GAP-43 protein. Such synthesis appears to correlate with axonal growth during maturation and regrowth after axotomy. In most adult neurons, the sharp decline in GAP-43 gene expression implies a reduced capacity for axonal growth. Neurons capable of extending axonal knobs in the absence of injury may indicate a "plasticity" underlying dynamic processes of interaction between neurons and their synaptic targets. Antisense and sense (control) riboprobes were used on serial sections in the three principal axes, and the magnitude of hybridization signal was examined to determine regional patterns. GAP-43 mRNA levels are pronounced in diverse neuronal groups including the locus coeruleus, raphé nn., dopaminergic nigral and ventral tegmental nn., mitral cells, hippocampal CA3, inferior olivary n., vagal motor n. and other parasympathetic preganglionic neurons, select thalamic midline and intralaminar nn., several specific nn. of the hypothalamus and basal forebrain, the granular layer of cerebellar cortex, the infragranular neocortex, and the granular olfactory paleocortex; there is a substantial range in the magnitude of expression. Regions revealing minimal signal include most thalamic sensory relay nuclei, the granule neurons of the olfactory bulb and dentate gyrus, and the caudate and putamen. Possible concomitants of GAP-43 expression include regulation of ion flux and neurotransmitter release. Those neurons with long, extensively dispersed and numerous synaptic connections display the strongest signals and may possess the greatest propensity for continuous growth and turnover of their axon terminals, in contrast to short-axon and specific projection neurons exhibiting minimal levels. These data may enable inferring which populations display normal or experimentally induced axonal growth.
通过原位杂交放射自显影技术，研究了成年大鼠脑内轴突生长相关蛋白GAP - 43的基因表达区域分布，以确定合成GAP - 43蛋白的成熟神经元群体的特征。这种合成似乎与成熟过程中的轴突生长以及轴突切断后的再生相关。在大多数成年神经元中，GAP - 43基因表达的急剧下降意味着轴突生长能力的降低。在未受伤情况下能够延伸轴突小结的神经元可能暗示了神经元与其突触靶点之间动态相互作用过程中的“可塑性”。在三个主要轴向上的连续切片上使用反义及正义（对照）核糖探针，并检测杂交信号的强度以确定区域模式。GAP - 43 mRNA水平在多种神经元群体中显著，包括蓝斑、中缝核、多巴胺能黑质和腹侧被盖核、二尖瓣细胞、海马CA3、下橄榄核、迷走运动核和其他副交感神经节前神经元、特定的丘脑中线和板内核、下丘脑和基底前脑的几个特定核、小脑皮质颗粒层、颗粒下新皮质以及颗粒状嗅古皮质；表达强度存在很大差异。显示最小信号的区域包括大多数丘脑感觉中继核、嗅球和齿状回的颗粒神经元以及尾状核和壳核。GAP - 43表达的可能伴随情况包括离子通量和神经递质释放的调节。与轴突短和特定投射神经元显示的最低水平相比，那些具有长的、广泛分散且众多突触连接的神经元显示出最强的信号，并且可能具有轴突终末持续生长和更新的最大倾向。这些数据可能有助于推断哪些群体表现出正常或实验诱导的轴突生长。
