Integrated assessment of continuous uroflow cystometry and visceromotor responses to bladder distension in urethane-anesthetized mice

Abstract

Bladder-related disorders, such as underactive or overactive bladder and chronic pelvic pain syndromes, are typically studied by recording cystometrogram and visceromotor responses (VMRs) to urinary bladder distension (UBD) in anesthetized rats. Recently, similar studies have been conducted in mice due to their suitability for genetic manipulation. However, assessing bladder physiology and pain in aged mice remains challenging due to inconsistencies in anesthesia. Here, we optimized a urethane anesthesia protocol to enable robust cystometrogram (CMG) recordings and VMR in female mice of 2 different age groups: mature (10-12 months) and aged (18-22 months). Mice were first anesthetized with 1.75% isoflurane inhalation for the surgical implantation of a bladder catheter and stainless-steel wire electrodes to the external oblique musculature for delivering bladder distension and recording muscular response respectively. Another catheter was placed intraperitoneally for continuous delivery of urethane (0.15-0.23 g/kg per hour for 2 hours). CMG was measured by delivering slow bladder filling (1.5 mL/h) through the catheter while recording intravesical pressure, VMR responses from external oblique musculature, and micturition volume. Afterwards, VMR response to UBD was recorded. In another cohort, both CMG and VMR response to UBD were assessed before and after intravesical infusion of 0.5% acetic acid and 0.1% lidocaine. Intravesical infusion of acetic acid significantly enhanced the VMR to grader bladder distension and disrupted the regular micturition cycles, which were normalized by intravesical lidocaine. This anesthesia protocol produced robust CMG and VMR recordings for 2 hours in mice of both age groups, enabling focused studies to advance mechanistic understanding of bladder-related disorders. SIGNIFICANCE STATEMENT: A urethane anesthesia protocol was optimized for robust cystometrogram and visceromotor response recordings in mature and aged mice. This model allows assessment of bladder physiology and pain, demonstrating that acetic acid disrupts micturition and enhances pain responses, which lidocaine normalizes.

Keywords: Cystometrogram; Cystometry; Intravesical; Urinary bladder distension; Visceromotor response.