Diurnal Variation in Urodynamics of Rat

Abstract

In humans, the storage and voiding functions of the urinary bladder have a characteristic diurnal variation, with increased voiding during the day and urine storage during the night. However, in animal models, the daily functional differences in urodynamics have not been well-studied. The goal of this study was to identify key urodynamic parameters that vary between day and night. Rats were chronically instrumented with an intravesical catheter, and bladder pressure, voided volumes, and micturition frequency were measured by continuous filling cystometry during the light (inactive) or dark (active) phases of the circadian cycle. Cage activity was recorded by video during the experiment. We hypothesized that nocturnal rats entrained to a standard 12:12 light:dark cycle would show greater ambulatory activity and more frequent, smaller volume micturitions in the dark compared to the light. Rats studied during the light phase had a bladder capacity of 1.44±0.21 mL and voided every 8.2±1.2 min. Ambulatory activity was lower in the light phase, and rats slept during the recording period, awakening only to urinate. In contrast, rats studied during the dark were more active, had a lower bladder capacities (0.65±0.18 mL), and urinated more often (every 3.7±0.9 min). Average bladder pressures were not significantly different between the light and dark (13.40±2.49 and 12.19±2.85 mmHg, respectively). These results identify a day-night difference in bladder capacity and micturition frequency in chronically-instrumented nocturnal rodents that is phase-locked to the normal circadian locomotor activity rhythm of the animal. Furthermore, since it has generally been assumed that the daily hormonal regulation of renal function is a major driver of the circadian rhythm in urination, and few studies have addressed the involvement of the lower urinary tract, these results establish the bladder itself as a target for circadian regulation.

Involvement of urinary bladder Connexin43 and the circadian clock in coordination of diurnal micturition rhythm

“…It has been reported that micturition shows a diurnal change in rodents as well as in humans 8,22,28,29 , although the day-night change is inverted because of the difference in diurnal versus nocturnal habits. However, it is unknown whether these changes are induced by an endogenous oscillator or only by a reflection of external light-dark changes.…”

Ketamine-induced ulcerative cystitis and bladder apoptosis involve oxidative stress mediated by mitochondria and the endoplasmic reticulum

“…A voiding contraction was defined as an increase in bladder pressure that resulted in urine loss. Peak micturation pressure was the maximum pressure during micturation as observed in CMGs (24).…”

Enhanced Susceptibility to Urinary Tract Infection in the Spinal Cord-Injured Host with Neurogenic Bladder

“…By 14 days postinjury, residual urine volumes had stabilized at a mean of ϳ2.94 ml (range, 0.15 ml to 10.6 ml), which is approximately twice the bladder capacity of spinal cord-intact rats (15). Notably, mean residual urine volumes in SCI rats remain stable at ϳ2.5 to 3.0 ml for at least an additional 2 weeks (i.e., up to 4 weeks post-SCI; data not shown).…”