Objective: To develop an in vitro model to allow electrophysiological recordings from pelvic nerve afferents of the urinary bladder in the rat and to ascertain the stability and reproducibility of the model with time.
Materials and methods: Six male Wistar rats (body weight approximately 100 g) were used in the study. The bladder (complete with accessory organs of prostate and seminal vesicles), urethra and penis, together with the attached pelvic nerve and L6/S1 nerve trunk, were removed intact and placed in a specially designed recording chamber containing oxygenated Krebs solution maintained at 30 degrees C. The bladder was catheterized urethrally and attached to a continuous-infusion pump and a pressure transducer. The L6/S1 nerve trunk was placed across a silicone-gel wall into a separate chamber containing liquid paraffin, in which multiunit recordings from pelvic nerve afferents originating from the bladder were made. The afferent nerve activities in response to repeated bladder distension with saline, at 0.04 mL/min for 8 min over 3 h, were compared using the paired t-test to assess the reproducibility of the model. Conduction velocity studies were also carried out to ascertain the proportion of C- and A delta-fibres in the multiunit recordings.
Results: Repeated bladder distension with saline over 3 h produced consistent and reproducible afferent nerve responses, signifying that the afferent nerves recorded in this study neither sensitize nor desensitize over time. This is an essential prerequisite when using this model to study the effects of pharmacological manipulation of the bladder on its afferent nerve response. Conduction velocity studies showed that approximately 30% of the afferent fibres recorded from were C-fibres with the remaining being A delta-fibres.
Conclusions: An in vitro bladder pelvic nerve afferent model for the rat was developed successfully; it is stable and produces reproducible results with repeated bladder distension over at least 3 h.