Fonnum F, Maehlen J, Njå A
J Physiol. 1984 Feb;347:741-9. doi: 10.1113/jphysiol.1984.sp015093.
Intact preganglionic axons can sprout and form new functional synaptic connexions with neurones in the partially denervated superior cervical ganglion of the guinea-pig (Maehlen & Njå, 1981). In the present work we have examined to what extent the degree of sprouting, as measured by intracellular recording, is paralleled by changes in ultrastructural and neurochemical parameters. The mean number of preganglionic axons innervating each neurone, as estimated by intracellular recording from ganglion cells during stimulation of the individual ventral roots, was reduced from about eleven to about two immediately after the partial denervation. However, 5-7 weeks after the operation, when sprouting was complete, each neurone was innervated on average by about seven axons. The estimated mean amplitude of the synaptic potential elicited by each innervating axon (about 5 mV) was only slightly increased after sprouting. Counts of the number of synaptic profiles per unit area of electron microscopical sections of the ganglion were reduced to about 15% of normal 3-4 days after the operation, and increased to about 60% of normal after sprouting (5-7 weeks). The activity of the enzyme choline acetyltransferase was about 20% of the normal value in ganglia examined 3-4 days after partial denervation. After sprouting (5-7 weeks), this value was increased to about 35% of that in normal ganglia. These results show that intact preganglionic sympathetic axons have a substantial growth potential. However, the increase in the choline acetyltransferase activity was smaller than the increase in electrophysiological and ultrastructural measurements. Therefore, compensatory axonal branching and synapse formation may cause a reduction in the supply of choline acetyltransferase to each presynaptic terminal from the parent soma.
完整的节前轴突能够发芽，并与豚鼠部分去神经支配的颈上神经节中的神经元形成新的功能性突触连接（梅伦和尼亚，1981年）。在本研究中，我们研究了通过细胞内记录测量的发芽程度在多大程度上与超微结构和神经化学参数的变化平行。通过在刺激单个腹根时对神经节细胞进行细胞内记录估计，支配每个神经元的节前轴突平均数量在部分去神经支配后立即从约11根减少到约2根。然而，在手术后5 - 7周，当发芽完成时，每个神经元平均由约7根轴突支配。发芽后，由每个支配轴突引发的突触电位的估计平均幅度（约5 mV）仅略有增加。神经节电子显微镜切片每单位面积的突触轮廓数量在手术后3 - 4天减少到正常的约15%，发芽后（5 - 7周）增加到正常的约60%。在部分去神经支配后3 - 4天检查的神经节中，胆碱乙酰转移酶的活性约为正常值的20%。发芽后（5 - 7周），该值增加到正常神经节的约35%。这些结果表明，完整的节前交感神经轴突具有显著的生长潜力。然而，胆碱乙酰转移酶活性的增加小于电生理和超微结构测量的增加。因此，代偿性轴突分支和突触形成可能导致从母细胞体向每个突触前终末供应的胆碱乙酰转移酶减少。
