Abstract: Objective To study the effects of nitroglycerin on urethral sphincter of chronic complete spinal cord injury female rats in vitro. Methods 30 SD female rats with 3 months old were transected at T10 spinal cord. After 8 weeks, the 10 rats with BBB scores ≤5 were selected as experimental group, and other 10 normal rats as control group. The difference of tension in both proximal segment (urethral smooth muscle strips) and distal segment (external urethral sphincter muscle strips) were surveyed before and after nitroglycerin 0.5 mg administration in bath. Results The tension of distal segment in control group reduced from (640.50±91.79) mg to (597.50±92.61) mg, and from (485.50±68.94) mg to (459.90±69.51) mg in experimental group. The difference between proximal segment and distal segment were (222.30±12.14) mg and (42.00±7.86) mg before and after administration in control group, and were (223.00±15.78) mg and (25.60±5.17) mg in experimental group. Conclusion The administration of nitroglycerin 0.5 mg in bath can reduce the tension of both urethral smooth muscle and external urethral sphincter in both normal and spinal cord injured rats. The relaxative effect on external urethral sphincter muscle of normal rats exceed that of injured ones, but approximate on urethral smooth muscle.

Key words: spinal cord injury, urethral smooth muscle, external urethral sphincter, nitroglycerin, nitric oxide, rats