Ganglionectomy in the adult male rat increases neuronal size and synaptic density in remaining contralateral major pelvic ganglion

This study aimed to characterize ganglion hypertrophy in the major pelvic ganglion (MPG) of male rats after contralateral ganglionectomy. Eighteen adult male Sprague-Dawley rats were used in this study. Nine of them were subjected to long-term (6 weeks) contralateral ganglionectomy, and nine were used as a control group. Six weeks postoperatively, the animals were euthanized and the MPG was identified and removed completely with its accessory ganglia and the associated nerves. The ganglia were then studied at the light microscope level using acetylcholinesterase histochemistry and synaptophysin immunohistochem-istry, and at the ultrastructural level using transmission electron microscopy. To assess the size of ganglionic neurons, morphometric analysis was done at the light microscope level of sections of resin-embedded pelvic ganglia. No shift was found in location of remaining ganglion after contralateral ganglionectomy. The remaining ganglion was larger and more elongated dorso-ventrally. Morphometric analysis done using semi-thin and thin sections revealed an increase in the neuronal size and expansion of synaptic connections of the con-tralateral ganglionectomy over the control, but there was no evidence of increased neournal number following contralateral ganglionectomy, despite the fact that it was found that after few weeks post contralateral ganglionectomy the remaining ganglion extended its innerva-tions to cover the opposite side which was innervated by the excised ganglion. We demonstrated the occurrence of hypertrophy in the neurons of the pelvic ganglion in the adult male rats, and that this hyperatrophy was a result of increase in neuronal size rather than number. This study has paved the way for investigating the mechanisms underlying neu-ronal hypertrophy, such as the role of cellular signaling processes and neurotrophic factors involved in pelvic neuron plasticity.