Background Voltage-gated K+channel(KV)plays a critical role in the modulation of detrusor contraction.This study was conducted to investigate the expressions of Kv2.1 and Kv2.2 in rat bladder with detrusor hyperreflexia(DH).Methods Thirty adult female Sprague-Dawley rats(200-220 g)were randomly divided into the control group and the experimental group.The experimental group was subjected to spinal cord injury(SCI).In the controls,the surgical procedure was identical with the exception that dura and spinal cord were transected.Four weeks after SCI,in vivo cystometry and mechanical pulling tests of isolated detrusor strips were performed.mRNA was extracted from the detrusors of normal and DH rats for the detection of expression of Kv2.1 and Kv2.2 by RT.PCR.Differences in expression between normal and overactive detrusors were identified by gel imaging.Results Fourteen rats in the experimental group exhibited uninhibited bladder contraction(>8 cmH20)before voiding after SCl.One rat died from infection.The frequency of DH in the experimental group was significantly different from that in the control group with or without treatment with 4-aminopyridine(4-AP)(P