PURPOSE: Overactive bladder is especially common in the elderly, although it is not regarded as a normal part of aging. Thus, we investigated how aging alters the cystometric and detrusor overactivity (DO) parameters and the density of nerve growth factor (NGF) in awake spontaneous hypertensive rats (SHRs) of different ages. METHODS: Three age groups of 12- (n=5), 17- (n=6), and 21- (n=6) week-old SHRs (Oriental Bio Inc.) 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). Of the IVP elevations above 2 cm H2O, DO was defined as a rise in IVP without a simultaneous change in IAP and was counted during the filling phase. We measured the expression of NGF in the bladders by enzyme-linked immunosorbent assay. RESULTS: Both the body and bladder weights significantly increased with age, but the normalized ratio between those was not changed. As for DO, none of the12-week-old rats showed DO, whereas the other groups did. DO increased significantly with age (P=0.0045 by Mantel-Haenszel trend test), although no significant differences were found in DO frequency or pressure between the 17- and 21-week-old age groups. NGF did not show any significant differences among the three groups. CONCLUSIONS: Our results showed that SHRs begin to shows DO after a certain age, such as 12 weeks of age, and that the occurrence of DO has a close relationship with aging. However, NGF, which is known to be increased in the bladder wall of patients with overactive bladder, did not show any relationship with aging in this study.
Abdominal Cavity ; Aged ; Aging ; Animals ; Catheters ; Humans ; Nerve Growth Factor ; Rats ; Rats, Inbred SHR ; Urinary Bladder ; Urinary Bladder, Overactive ; Urodynamics ; Weights and Measures

PURPOSE: To compare the physical characteristics of detrusor overactivity (DO) induced by intravesical infusion of saline in awake, sham rats and rats with chronic spinal cord injury (SCI), by simultaneous registrations of intravesical and intraabdominal pressures. METHODS: Male Sprague-Dawley rats, normal or with a spinal vascular clip at the level of Th9, were investigated cystometrically 1 and 4 weeks after SCI. Intra-vesical pressure (IVP) and intra-abdominal pressure (IAP) were recorded simultaneously to evaluate true DO. During the filling phase, the event of IVP rises, defined as increments that exceeded 2 cmH2O from baseline, were determined as DO according to the absence of simultaneous changes in IAP. RESULTS: All SCI rats exhibited DO during the filling phase, which was not shown in sham rats. The frequency and pressure of DO had a tendency to decrease with time. The DO frequency of SCI rats after 4 weeks (0.9+/-0.2 min(-1)) was decreased compared with that after 1 week (2.1+/-0.4 min(-1); P<0.05). The DO pressure of SCI rats after 4 weeks (8.4+/-1.9 cmH2O) was decreased compared with that after 1 week (11.6+/-2.9 cmH2O; P>0.05). CONCLUSIONS: Cystometric studies in awake male SCI rats showed some significant changes in bladder function after SCI. All SCI rats exhibited DO during the filling phase, and showed different physical characteristics of DO over the course of time. The neurological basis of these time-related changes remains poorly understood, but may provide important prognostic information about long-term urological management in SCI patients.
Animals ; Humans ; Male ; Rats ; Rats, Sprague-Dawley ; Salicylamides ; Spinal Cord ; Spinal Cord Injuries ; Urinary Bladder ; Urinary Bladder, Overactive ; Urodynamics