Axotomy-induced alterations in the electrophysiological characteristics of neurons

摘要: The electrophysiological alterations provoked by axotomy have now been studied for almost half a century, in number of different cell types. Consequently, it is possible to detail some common mechanisms underlying these changes and sort out certain trends the data. major phenomena reviewed this section future directions are summarized below. (1) It advance unified hypothesis effects on conduction velocity myelinated fibers. key that axon diameter, which directly correlated with velocity, regulated, at least part, neurofilament protein gene expression transport into axon. Thus, largest axons, fastest velocities, highest contents, turn, experience greater or faster declines content, caliber, speed following nerve injury. This regulation also appears be target- and/or accessory cell-dependent. In fact, Hoffman colleagues (1988) hypothesized neuron interactions specific targets (via as yet unknown target-induced signals) may either specify permit specification level neurons. Imposed primary size determinant an influence activity, underlies differential atrophy decrement exhibited motor sensory fibers comparable diameters same lesioned nerve. Unmyelinated whose structures not dominated content metabolism, react very differently axotomy. structural metabolic basis their reaction known. (2) Passive membrane properties, particular neuronal input resistance, remain relatively stable majority neurons after exceptions, vertebrate spinal motoneurons, lamprey dorsal interneurons, mammalian vagal all show increase resistance change geometric simplification dendritic trees real apparent one case reduction body other two; however, cannot excluded even latter two cases. more pronounced those most extensive complex geometries (i.e. F-type motoneurons). More combined (ideally under voltage patch clamp conditions) morphological investigations single need done resolve questions.(ABSTRACT TRUNCATED AT 400 WORDS)