Fig 1: The expression and functional activity of pain- and itch-related receptor MrgprD are upregulated in DRG neurons from oxazolone-induced ACD model mice. A Heatmap showing the expression of Mrgpr family genes identified in DRG of oxazolone versus control group mice. n = 4 mice per group. B qPCR validations of the expression of three itch- or pain-related Mrgpr genes, namely, Mrgprx1, Mrgpra3, and Mrgprd. n = 6–8 mice per group. *p < 0.05, **p < 0.01 versus control group. C Representative immunofluorescence images indicating MrgprD antibody staining of DRGs from control and oxazolone group of mice. Scale bar is 50 µm. Areas staining positive for MrgprD are shown in green. NeuN staining (red) was used to illustrate DRG neurons. D Summarized percentages of MrgprD+ neurons per field. The total neuronal cell numbers were deduced from NeuN+ staining. n = 6 mice per group. **p < 0.01 versus control group. E Pseudo-color images of Fura-2-based ratiometric Ca2+ imaging of C1–T1 DRG neurons from oxazolone and control group of mice in response to endogenous MrgprD-specific agonist ß-alanine (8 mM). At the end of all recordings, 40 mM KCl was perfused to trace all alive neurons. F Summary of the percentages of neurons responding to ß-alanine challenge. G Summary of ? increase in peak 340/380 ratio upon ß-alanine challenge. n = 7 tests per group. Each group included 200–300 neurons. *p < 0.05, **p < 0.01 versus control group. H Representative Ca2+ traces of DRG neurons in response to ß-alanine and KCl from oxazolone and control group of mice. I Protocol for behavioral studies. J The effect of different dosages of ß-alanine (10, 30, and 100 mM in 50 µl) on scratching behaviors in naïve mice. Beta-alanine was subcutaneously injected into the neck of naïve mice. Vehicle group received PBS injection. **p < 0.01 as indicated. NS, no significance. K Summary of scratching bouts upon vehicle/ß-alanine (30 mM) injection in control or oxazolone group of mice. n = 6–7 mice per group