Changes of bladder activity and glycine levels in the spinal cord and serum after spinal cord injury in rats

We examined whether the glutamate and glycine levels in the central nervous system (CNS) were related to bladder activity and their serum levels in rats after spinal cord injury (SCI). Female rats were anesthetized with halothane, and the spinal cord was completely transected at the lower thoracic level. At I day to 8 weeks after SCI, bladder activity and the glutamate and glycine levels in the CNS and serum were measured. Urinary retention was observed in the acute period after SCI. Isovolumetric cystometry showed no bladder contractions at 1 and 3 days after SCI, but contractions were seen after 2 to 8 weeks. The glycine level was increased in the lumbosacral cord at I day after SCI, but it was decreased at 2 to 8 weeks. The serum glycine level was also increased at 1 week after SCI, and it was decreased gradually over 4 to 8 weeks. The glutamate level in each CNS region and serum of SCI rats did not differ from those of control rats and sham-operated rats at I day to 8 weeks after surgery. Therefore, the change of the glycine level in the lumbosacral cord may influence bladder contractions and its serum level after SCI.