The effect of lumbar spinal nerve (SN) transection on estimates of neuron number was investigated in the dorsal root ganglia (DRGs) of juvenile bullfrogs (Rana catesbeiana). SN8 and SN10 were transected on one side, and SN9 was left intact. Two weeks after nerve injury, estimates of neuron number in
Neuron addition during growth of the postmetamorphic bullfrog: Sensory neuron and axon number
β Scribed by Meeker, Marianne L.; Farel, Paul B.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 614 KB
- Volume
- 389
- Category
- Article
- ISSN
- 0021-9967
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β¦ Synopsis
Neuron addition is one means whereby the nervous system can compensate for increased body size. Neurons can be added either by mitosis of stem cells or by late differentiation of committed precursors. Previously, the doubling of hind limb dorsal root ganglion (DRG) neurons in postmetamorphic bullfrogs (Rana catesbeiana) was found to occur in the absence of neuron proliferation (St. Wecker and Farel [1994] J. Comp. Neurol. 342:430-438). In the present study, we identify a population of cells in the DRGs of juvenile frogs that lack the appearance typical of sensory neurons yet are immunoreactive to a neuron-specific probe for neurofilament protein. These less differentiated (type-L neurons) could not be labeled retrogradely with horseradish peroxidase from the periphery or dorsal root. Despite their apparent immaturity, type-L neurons appear to have extended axons both centrally and toward the periphery, because axon number in dorsal roots and peripheral nerves was similar in juvenile and adult frogs. These findings are consistent with the existence in juvenile frogs of a population of incompletely differentiated DRG neurons that lack the physiological properties and appearance typical of mature neurons.
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