Cystometry experiments

Cystometric investigations were performed in conscious rats. As previously described [8], the rats were placed in metabolic cages and the free tip of the bladder catheter was connected to a pressure transducer for bladder pressure monitoring and to a syringe pump for bladder perfusion. The rats were allowed an acclimation period then the bladder was continuously perfused with saline at 50 μl/min. Weighing devices placed underneath the metabolic cages were used to quantify the micturition volumes. Once the bladder continuous perfusion started, a 60-min stabilization period was considered to ensure reproducible micturition cycles i.e., the variations in micturition volumes and in intervals between micturition did not exceed ±10%, before starting a 60-min evaluation period. During this evaluation period, intravesical pressure was recorded and the following parameters related to voiding contractions were measured: maximal amplitude, baseline intravesical pressure, micturition pressure threshold and intercontraction interval for reflex-evoked bladder micturition. Also, frequency of non-voiding contractions and the volume threshold to elicit non-voiding contractions for each cycle during the filling phase were measured (Fig. 1). Furthermore, the infused volume between two voiding contractions, index of the bladder capacity, and the voided volume of each voiding contraction were analyzed, and the mean urine flow rate was assessed.

Illustration of the parameters computed for bladder voiding and non-voiding contractions during cystometry in a conscious of SHR-testosterone treated rat. MAVC: maximal amplitude of voiding contractions, BP: baseline intravesical pressure, PT: micturition pressure threshold, ICI: intercontraction interval. FNVC: frequency of non-voiding contractions, VT: volume threshold to elicit non-voiding contractions for each micturition cycle during the bladder filling phase