The same dorsal root ganglion neurons innervate uterus and colon in the rat

The purpose of this study was to determine whether primary sensory neurons that innervate the uterus receive convergent input from the colon. To test this, in the rat, cell bodies of colonic and uterine dorsal root ganglia were retrogradely labeled with fluorescent tracer dyes microinjected into the colon/rectum and bilaterally into the uterine horns. Ganglia were harvested, cryoprotected and cut into 20 mu m slices to identify positively stained cells for fluorescent microscopy. Up to 5% of neurons were colon-specific or uterus-specific, and 10-15% of labeled ganglion neurons innervate both viscera in the L-1, L-2, L-6 and S1-S3 levels. These results suggest a novel form of visceral sensory integration in the dorsal root ganglion that may underlie comorbidity of many functional pain syndromes.