Transient Receptor Potential Vanilloid Type 1 (TRPV1) is a major nociceptive ion channel implicated in bladder physiology and/or pathophysiology. However, the precise expression of TRPV1 in neuronal versus non-neuronal bladder cells is uncertain. Here we used reporter mouse lines (TRPV1-Cre:tdTomato and TRPV1PLAP-nLacZ) to map the expression of TRPV1 in post-natal bladder. TRPV1 was not detected in the urothelium, however, we found marked expression of TRPV1 lineage in sensory nerves, and surprisingly, in arterial/arteriolar smooth muscle (ASM) cells. Tomato fluorescence was prominent in the vesical arteries and in small diameter (15 to 40 μm) arterioles located in the sub-urothelial layer with a near equal distribution in bladder dome and base. Notably, arteriolar TRPV1 expression was greater in females compared with males and increased in both sexes after 90 days of age suggesting a sex-hormone and age dependence. Analysis of whole bladder and vesical artery TRPV1 mRNA revealed a similar sex and developmental dependence. Pharmacological experiments confirmed functional TRPV1 protein expression; capsaicin increased intracellular Ca2+ in approximately 15% of ASM cells from wild-type female bladders but we observed no responses to capsaicin in bladder arterioles isolated from TRPV1-null mice. Further, capsaicin triggered arteriole constriction that was rapidly reversed by the TRPV1 antagonist, BCTC. These data show that bladder ASM cells, predominantly in post-pubertal female mice, express functional TRPV1 channels that may act to constrict arterioles. TRPV1 may therefore play an important role in regulating the microcirculation of the female bladder and this effect may be of significance during inflammatory conditions.
- Copyright © 2016, American Journal of Physiology-Renal Physiology