A novel in vitro bladder pelvic nerve afferent model in the rat

Objective To develop an in vitro model to allow electrophysiological record ings from pelvic nerve afferents of the urinary bladder in the rat and to a scertain the stability and reproducibility of the model with time. Materials and methods Six male Wistar rats (body weight approximate to 100 g) were used in the study. The bladder (complete with accessory organs of p rostate and seminal vesicles), urethra and penis, together with the attache d pelvic nerve and L6/S1 nerve trunk, were removed intact and placed in a s pecially designed recording chamber containing oxygenated Krebs solution ma intained at 30 degrees C. The bladder was catheterized urethrally and attac hed to a continuous-infusion pump and a pressure transducer, The L6/S1 nerv e trunk was placed across a silicone-gel wall into a separate chamber conta ining liquid paraffin, in which multiunit recordings from pelvic nerve affe rents 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 reprod ucibility of the model, Conduction velocity studies were also carried out t o ascertain the proportion of C- and A delta-fibres in the multiunit record ings. Results Repeated bladder distension with saline over 3 h produced consisten t and reproducible afferent nerve responses, signifying that the afferent n erves recorded in this study neither sensitize nor desensitize over time, T his is an essential prerequisite when using this model to study the effects of pharmacological manipulation of the bladder on its afferent nerve respo nse. Conduction velocity studies showed that approximate to 30% of the affe rent fibres recorded from were C-fibres with the remaining being A delta-fi bres. Conclusions An in vitro bladder pelvic nerve afferent model for the rat was developed successfully: it is stable and produces reproducible results wit h repeated bladder distension over at least 3 h.