Limitations in using rabbit bladders in electrophysiological and urodynamic experiments

The aim of this study was to explore the possibility of using rabbit bladder as a model for experimental detrusor electrostimulation research. In a study of urinary bladder activity induced through electrostimulation of the ventral roots, the functional and morphological parameters of the rabbit detrusor were investigated. Under general anaesthesia, open electrostimulation of ventral spinal roots leading towards the detrusor (usually S2, S3) was performed in 20 rabbits. Detrusor response was recorded by repeated electromyography and cystometry in two groups: animals with naturally concentrated urine content (Group A, eight rabbits) and animals after flushing and filling the bladder with saline (Group B, 12 rabbits). Histological examination of bladder wall was performed in both groups. The measured values were compared to one another as well as with data from the veterinary and human literature. The histological specimens were compared with histological specimens of human bladder. The reaction of detrusor fibres was detectable by electromyography in all cases. Elevation of intravesical pressure as a consequence of detrusor contraction was more difficult to detect, as this depends more on the density of the intravesical content. The pressure rise in Group B had a higher amplitude - up to 15 cm H2O versus 5 cm H2O in the first group (P = 0.00046). Histological examination of bladder wall from the two groups of rabbits showed no differences. In comparison with the bladder wall in humans, the only differences found were significantly thinner detrusor layers relative to the overall thickness of bladder wall. It is possible to use rabbit bladder for research into experimentally electrostimulation-induced activity of the detrusor or for experimental detrusor reinnervation research. It is necessary, however, to take into account certain limits - the lower contractility of the bladder wall and the need for qualitative control of bladder content. The present results also suggest that the physiological micturition of rabbits is probably more dependent on abdominal pressure than in humans.