Continence · Oct 21, 2026
A pilot study on the impact of age on pain induced by Water Avoidance Stress in female and male Wistar Han rats
By Pereira L, Santos-Pereira M, Santos-Leite L et al.
Background and Objective Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a condition that changes with age. Integrating age as a biological variable in preclinical models is critical for translational validity. This study investigated whether aging modulates pain and bladder activity in a rat model of pelvic pain induced by Water Avoidance Stress (WAS). Methods Thirty Wistar Han rats (females: 6-7, 15-18, 23-25 months; males: 6-7, 23-25 months) were randomized into age- and sex-specific groups. Females with 15-18 months underwent ovariectomy. Animals were exposed to WAS (1 h/day for 10 days) and assessed at baseline and post-WAS. Ongoing and evoked pain were evaluated using the Rat Grimace Scale, mechanical thresholds (Von Frey), and thermal sensitivity (Hargreaves) at the genital/thigh and hind paw. Spontaneous bladder activity was assessed using the Voiding Spot Assay. Effect size (Hedges’ g z ) and confidence interval (CI) were calculated, alongside paired comparisons. Key Findings and Limitations Younger animals exhibited pain-like behaviors and genital/thigh sensitization, whereas old animals presented heterogeneous or minimal responses. VSA findings suggested an increase in low-volume spots in younger groups. Conclusions and Clinical Implications: Genital/thigh’s mechanical hypersensitivity indicates bladder-related pain mechanisms in the WAS model. Older rats exhibited fewer signs of pain in the WAS paradigm than younger rats. Findings support the need to refine age-inclusive models and improve bladder-specific behavioral metrics.