EFFECT OF AGING ON CYSTOMETRIC PARAMETERS AND DETRUSOR OVERACTIVITY CHARACTERISTICS IN AWAKE SPONTANEOUS HYPERTENSIVE RATS

초록

Hypothesis / aims of study The overactive bladder (OAB) syndrome and detrusor overactivity (DO) is especially common in the elderly, although these conditions are not regarded as a normal part of aging [1]. The spontaneous hypertensive rat (SHR) is considered a valuable tool to study the pathogenesis of DO, which is still unknown. We investigated how aging alters the cystometric DO parameters and the density of nerve growth factor (NGF) in awake SHRs of different ages. Study design, materials and methods Three age groups of 12 (n=5), 17 (n=6), 21 (n=6) week-old SHRs (Oriental Bio Inc, Gyeonggi-Do, Korea) were used. A catheter was implanted into the bladder to record the intravesical pressure (IVP), and a balloon-fitted catheter was positioned in the abdominal cavity to record the intraabdominal pressure (IAP), as described previously [2]. Cystometric pressure- and volume-related parameters and DO-related ones during the filling phase were investigated. The detrusor pressure was defined as the IVP minus the IAP. DO was defined as a rise in IVP above 2 cm H2O during the filling phase, without a simultaneous change in IAP. The expression of NGF in the bladders was measured using ELISA. Results The body weight and bladder weight increased significantly with age, but the ratio between these parameters was not changed. Basal pressure significantly decreased with age, although there were no changes in threshold and maximal pressures. Micturition volume and micturition interval showed significant increases at ages between17 and 21 weeks,. There was no residual urine in any group. DO was not found in12 week-old rats, while the other groups showed DO (Fig. 1). Frequency and amplitude of DO tended to increase between 17 and 21 weeks, although the difference were not significant. NGF did not show any difference among three groups. Interpretation of results DO could be demonstrated in our strain of SHRs after 12 weeks of age, and there was a close relationship with aging.