[Experimental study on morphological changes of detrusor muscle and its neuromuscular junction after medullary cone...

To investigate the rule of the morphological changes of the detrusor muscle and its neuromuscular junction after the medullary cone injury in rats.

Forty-eight SD adult rats were divided into 6 groups randomly, each of which was 8. There were normal control group(group A), 4 weeks group (group B), 6 weeks group (group C), 8 weeks group (group D), 10 weeks group (group E) and 12 weeks group (group F) after the medullary cone injury respectively. The medullary cone injury was completed in the level of L4.5 with a sharp and transsectional way. The HE dyeing of the detrusor muscle was performed firstly to observe the changes of the section areas of muscle fibers. And the electron microscopic samples of the detrusor muscle were made to investigate the rules of the ultrastructructral changes in the detrusor muscle and its neuromuscular junction. Finally, the Masson trichromatic dyeing of the detrusor muscles was performed to calculate the percentages of the smooth muscle and the connective tissue.

The HE dyeing of the detrusor muscle indicated the section areas of muscle fibers in groups E, F was significantly less than that in group A (P<0.05). The gradually aggravated ultrastructructral changes of detrusor cells in groups B-F were observed in atonic bladders, such as various shape and size, malalignment, wide separation between muscle cells, abundant collagen fibrils and irregular dense structures between individual cells, obvious rough endoplasmic reticulum widen and mitochondrial edema were noted. And the ultrastructructral changes of the neuromuscular junctions manifested that the similar structures in group A and the reduction of the mitochondria and synaptic vesicles was seen in groups B, C and D, the conspicuous degenerative neuromuscular junction and the obvious reduction of the synaptic vesicles and the mitochondria was observed in group E, and the deteriorative degenerative neuromuscular junction and the obvious reduction or disappearance of the synaptic vesicles and the mitochondria even to the degenerative corpuscle was noted in group F. The Masson trichromatic dyeing in the detrusor muscles indicated that there were significant differences in the percentage of the connective tissue in the detrusor muscles between groups E, F and group A, and between group E and group F respectively (P<0.05).

The irreversible changes of the detrusor muscle and its neuromuscular junction can be seen in the 10th week after medullary cone injury in rat. And the nerve repairing procedures should be performed before this.