Postnatal neuron death in the nodose ganglia of the rat

Developmental neuron death is well described in sensory and sympathetic ganglia derived from the neural crest. In this study, nodose ganglia were removed from 2 litters of postnatal rats (male and female; 1, 3, 5, 9, and 14 days old) in order to determine whether postnatal neuron degeneration occurs in the nodose ganglia, which is derived from ectodermal placode. The ganglia were embedded in paraffin, sectioned and stained with methylene blue. Neuronal nuclei were counted at a magnification of 100 and diameters of nodose nuclei were traced at each age. There was a significant (p < 0.001) increase in the nuclear diameter of the nodose neurons of male and female rats from birth to postnatal day 14. In male rats, this difference was most marked between postnatal day 5 and postnatal day 14. The results of the neuron counts for both male and female rats indicated a gradual, significant (p < 0.001) decrease in the neuron population from day 1 to 14. For the males a 57.2% decline was observed, while the females displayed a 49.2% decline. The numbers of neurons in male and female ganglia showed no consistent differences. The data for neuron counts suggest that developmental neuron death occurs in postnatal rats with a gradual decrease in number of nodose neurons. However, since our findings show no evidence of degenerating nodose neurons, we are unable to rule out the possibility of migration from the developing ganglion.