[Morphological changes in major pelvic ganglion neurons and histological structure of bladder using rat model of partial urethral ligation].

Ninety six rats were divided into 4 groups (normal control group (N = 4), ligation group (N = 20), ligation-removed group (N = 36), and sham surgery group (N = 36)). The neuronal size of the 4-week ligated rats returned to normal 6 weeks after removal of the ligation. Rats ligated for 7, 11 and 20 weeks also exhibited a significant increase in the mean area but they could not make a complete recovery after removal of ligation for 6 weeks. Only the rats in the 1- and 4-week ligation groups could recover their neuronal size. Area densities of smooth muscle: connective tissue (ADsc ratio) was calculated using Elastica van Gieson staining sections of bladder strips. When ligation was removed, the ratio dropped and became nearly equal to the value of the sham surgery group. Only the 7-week group showed a lower ADsc ratio than the sham surgery group after the ligation was removed. These findings suggest that the reversibility of neuronal hypertrophy might become irreversible when the period of partial urethral ligation persisted beyond 7 weeks. Irreversible hypertrophy of major pelvic ganglion (MPG) neurons might be greatly related with the irreversibly enlarged fibrous bladder which could not show the same ADsc ratio as was seen in the sham surgery groups.