The production of ganglionic hypertrophy in Rana pipiens larvae

Abstract

AbstractThe periphery available to the ninth spinal ganglion of Rana pipiens larvae was effectively increased by the unilateral removal at stage V of two (8 and 10) of the three (8, 9 and 10) spinal ganglia which normally provide the bulk of the sensory innervation to the hindlimb. The levels of the resulting hypertrophy of the ninth ganglion were found to compare favorably with those produced by other workers using other techniques.The effect of peripheral increase on mitotic activity, nerve cell number, and neuronal size (as indicated by nuclear cross sectional area) was determined. Differences in nuclear cross sectional area between neurons in hypertrophic and control ganglia were not found to be significant; however, the interaction between peripheral increase and developmental stage was found to be significant, leaving open the possibility that neurons might temporarily respond to peripheral increase by increasing in size.Mitotic activity and neuronal numbers in ganglia with increased peripheries were greater than those in controls at all stages at which counts were made. It is concluded that either, or both, of two mechanisms could be active in producing the observed neuronal hyperplasia in hypertrophic ganglia. Daughter products from the increased numbers of mitoses could provide additional cells which differentiate to become neurons, or normally occurring neuronal loss could be reduced.Results are discussed in the context of current ideas dealing with the regulation of neuronal numbers.