Abstract
The increase of the peripheral area available for innervation by the ninth spinal ganglion of larval Rana berlandieri was accomplished by unilaterally removing at stage V two (numbers 8 and 10) of the three (numbers 8, 9, and 10) ganglia that normally provide the bulk of the sensory innervation to the hindlimb. Peripheral increase significantly enhanced nerve cell number, and the change in neuronal number with developmental stage was also significant. The increase in nerve cell numbers in affected ganglia of 86% over control values at stage XVI compares favorably with the results of workers using different techniques.
The effect of peripheral increase on normally occurring neuronal degeneration during the development of the hyperplastic condition through early and middle larval stages was determined. While the data show a trend toward the presence of fewer degenerating neurons in peripherally overloaded than in control ganglia through stage X, the differences in the numbers of dying nerve cells were not significant. This fact and other considerations suggest that a mechanism other than or in addition to a reduction in the level of neuronal degeneration must be operative to account for the increase in the number of neurons present in ninth ganglia with expanded peripheries.
Results are discussed in the context of the temporal pattern of the proliferation of cells that differentiate as neurons, the establishment of centralβperipheral connections, and neuronal degeneration.