A novel behavioral paradigm for odor-induced voluntary urination in mice.

Voluntary urination—the conscious control over urine release based on internal and external cues—is essential for social functioning and physiological homeostasis, yet the neural mechanisms underlying this behavior remain poorly understood. Effective mechanistic dissection requires genetically tractable models with robust naturalistic behaviors. However, C57BL/6J mice, despite their rich genetic toolkit, exhibit weak scent-marking unless subjected to prolonged social isolation, whereas BALB/c mice display robust marking but lack genetic accessibility. To bridge this gap, we employed F1 hybrid males (C57BL/6J × BALB/c) to combine these complementary strengths and established a 10-minute odor-driven paradigm in which both group-housed and socially isolated F1 males exhibited robust scent-marking toward estrous female urine. To facilitate efficient and accurate analysis of urine deposition from this behavioral paradigm, we trained a YOLOv8-based deep learning model for automated quantification, achieving high accuracy. Furthermore, whole-brain c-Fos mapping revealed significant activation in the prefrontal cortex, brainstem, and other key regions implicated in regulating this voluntary voiding behavior. Thus, our study establishes a novel behavioral paradigm for odor-induced voluntary urination, providing a genetically accessible model system to dissect the neural circuits governing physiological voiding and neurogenic lower urinary tract dysfunction.