Understanding the sensory mechanisms innervating the bladder is paramount to developing efficacious treatments for chronic bladder hypersensitivity conditions. The contribution of Mas-gene-related G protein-coupled receptors (Mrgpr) to bladder signaling is currently unknown. Using male and female mice, we show with single-cell RT-PCR that subpopulations of DRG neurons innervating the mouse bladder express MrgprA3 (14%) and MrgprC11 (38%), either individually or in combination, with high levels of coexpression with Trpv1 (81%-89%). Calcium imaging studies demonstrated MrgprA3 and MrgprC11 agonists (chloroquine, BAM8-22, and neuropeptide FF) activated subpopulations of bladder-innervating DRG neurons, showing functional evidence of coexpression between MrgprA3, MrgprC11, and TRPV1. In ex vivo bladder-nerve preparations, chloroquine, BAM8-22, and neuropeptide FF all evoked mechanical hypersensitivity in subpopulations (20%-41%) of bladder afferents. These effects were absent in recordings from Mrgpr-clusterD2/2 mice. In vitro whole-cell patch-clamp recordings showed that application of an MrgprA3/C11 agonist mixture induced neuronal hyperexcitability in 44% of bladder-innervating DRG neurons. Finally, in vivo instillation of an MrgprA3/C11 agonist mixture into the bladder of WT mice induced a significant activation of dorsal horn neurons within the lumbosacral spinal cord, as quantified by pERK immunoreactivity. This MrgprA3/C11 agonist-induced activation was particularly apparent within the superficial dorsal horn and the sacral parasympathetic nuclei of WT, but not Mrgpr-clusterD2/2 mice. This study demonstrates, for the first time, functional expression of MrgprA3 and MrgprC11 in bladder afferents. Activation of these receptors triggers hypersensitivity to distension, a critically valuable factor for therapeutic target development.
Bibliographical noteFunding Information:
Received Dec. 24, 2020; revised Feb. 28, 2021; accepted Mar. 6, 2021. Author contributions: L.G., A.C., and S.M.B. designed research; L.G., A.C., and S.G.-C. performed research; L.G., A.C., S.G.-C., J.C., A.M.H., and S.M.B. analyzed data; L.G., A.C., S.G.-C., D.G., N.J.S., X.D., J.C., A.M.H., and S.M.B. edited the paper; S.M.B. wrote the first draft of the paper; S.M.B. wrote the paper. X.D. is a cofounder of Escient Pharmaceuticals. All remaining authors declare no competing financial interests. This work was supported by National Health and Medical Research Council of Australia Project Grant APP1140297 to S.M.B., National Health and Medical Research Council of Australia R.D. Wright Biomedical Research Fellowship APP1126378 to S.M.B., and Australian Research Council Discovery Project DP180101395 to A.M.H. and S.M.B. pL.G. and A.C. contributed equally to this work. Correspondence should be addressed to Stuart M. Brierley at email@example.com. https://doi.org/10.1523/JNEUROSCI.0033-21.2021 Copyright © 2021 the authors
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- Sensory neurons
- Visceral afferents