Effect of Aging on Cystometric Parameters and Detrusor Overactivity Characteristics in Awake Spontaneous Hypertensive Rats

초록

Hypothesis / aims of study : The overactive bladder (OAB) is especially common in the elderly, although it is not regarded as a normal part of aging [1]. Spontaneous hypertensive rat (SHR) is considered a valuable tool to study the pathogenesis of OAB. Thus, we investigated how aging alters the cystometric/detrusor overactivity (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. Of the IVP rises above 2 cm H2O, DO was defined as a rise in IVP without a simultaneous change in IAP and counted during the filling phase. And we measured the expression of NGF in the bladders using ELISA. Results : The body weight and bladder weight significantly increased with age, but the ratio between those was not changed. Basal pressure significantly decreased with age, although there showed no changes in threshold and maximal pressures. As for the bladder capacity, micturition volume and micturition interval, there showed significant increase between 17 and 21 weeks, although these had no significance until 17 weeks. They showed no residual urine in all groups. As for the DO, all 12 week-old rats did not show DO at all, while the other groups showed the DO (Fig. 1). In terms of frequency and increased amplitude of the DO, there showed an increasing tendency in order of 17 and 21 weeks, although no significant difference was found between them. However, NGF did not show any difference among three