contraction-induced pain in mice

Uterine contraction-induced pain (UCP) represents a common and severe form of visceral pain. Nerve fibers that innervate uterine tissue express the transient receptor potential vanilloid channel 1 (TRPV1), which has been shown to be involved in the perception of UCP. The phosphoinositide-interacting regulator of TRP (Pirt) may act as a regula-tory subunit of TRPV1. The intraperitoneal injection of oxytocin into female mice after a 6-day priming treatment with estradiol benzoate induces writhing responses, which reflect the presence of UCP. Here, we first compared writhing response between Pirt+/+ and Pirt−/ − mice. Second, we examined the innervation of Pirt-expressing nerves in the uterus of Pirt−/ − mice by immunofluorescence and two-photon microscopy. Third, we identified the soma of dorsal root ganglion (DRG) neurons that innerve the uterus using retrograde tracing and further characterized the neuro-chemical properties of these DRG neurons. Finally, we compared the calcium response of capsaicin between DRG neurons from Pirt+/+ and Pirt−/ − mice. We found that the writhing responses were less intensive in Pirt−/ − mice than in Pirt+/+ mice. We also observed Pirt-expressing nerve fibers in the myometrium of the uterus, and that retrograde-labeled cells were small-diameter, unmyelinated, and Pirt-positive DRG neurons. Additionally, we found that the num-ber of capsaicin-responding neurons and the magnitude of evoked calcium response were markedly reduced in DRG neurons from Pirt−/ − mice. Taken together, we speculate that Pirt plays an important role in mice uterine contraction-induced pain