INTRODUCTION & OBJECTIVES: Autonomous activity in isolated bladders has been demonstrated in normal rat and guinea pig. To search for differences between the autonomous activity in normal and neurogenic bladders we investigated two groups of isolated rat bladders.
MATERIAL & METHODS: Animal experiments were approved by the Animal Ethical Committee of the KU Leuven. Two groups of rat bladders were investigated: a normal (n=7) and a neurogenic group (n=8), all derived from female Wistar rats, 250-350 g. Rats were spinalised at the vertebral level T8-T9 and sacrified at D21; bladders from the control group were investigated in the same period. Bladders were incubated in a constantly gassed Kreb?s solution, at 37 degrees Celcius. Intravesical pressure was measured after a prefilling of 200-400µl (volume found after sacrifying). Pressures were measured during 45 min, with 15 min of resting status, 15 min of filling status at a rate of 20µl/min and 15 min of resting status after filling phase. Pressures were measured with BD transducers (Becton-Dickinson®); these were calibrated before every experiment and replaced every five measurements. Recordings were done with Dataq software and hardware (Dataq® instruments) Quantification and qualification of the activity pattern was done by dividing pressures changes in groups: - Macrocontractions were defined as pressure changes of minimal 0.500 cmH20, lasting between 5 and 20 sec and ending when the pressure level has fallen to 25% of its original height. - Spikes were defined as pressure changes of minimal 0.100 cmH2O, lasting between 0 and 3 sec and ending when the pressure level has fallen with a minimal amount of 0.100 cmH2O Statistics were performed on the analysed pressure changes 5 min before and 5 min after the filling phase. A Mann-Whitney U test was used.
RESULTS: The amount of spikes 5 min before the filling phase was significant higher in the neurogenic group (p 0.0079); after the filling phase the amount was not significantly different (p 0.2222) The amount of macrocontractions 5 min before the filling phase was not significantly different (p 0.0555), the amount 5 min after the filling phase was significantly higher in the control group (p 0.0317). The amount of spikes/macrocontraction 5 min before and 5 min after the filling phase was significantly higher in the neurogenic group (p 0.0079 before, p 0.0079 after).
CONCLUSIONS: This is the first model to demonstrate preliminary that the pattern of autonomous activity in neurogenic bladders, derived from paraplegic rats, is mainly significantly different from the autonomous activity in normal bladders. We demonstrated a global overactivity in isolated neurogenic bladders, which was consistent after a constant filling phase. If this can be confirmed in larger series, this model can offer exciting new possibilities in the search for novel strategies in the treatment of bladder overactivity.