Changes in gene expression in P2Y1-/- mice. A. Changes in mRNA levels for TRPV1, P2X3 and the Gi-coupled P2Y receptors P2Y12, P2Y13 and P2Y14 in L2-5 DRG. Of the genes examined, only P2Y13 levels were significantly altered in P2Y1-/- mice, showing a 2.7-fold increase over wildtype levels (n = 5/genotype, *p < 0.001). B. P2Y13 protein levels were analyzed by multiplex Western blot using actin as a reference standard. Quantification of band density revealed no significant difference in P2Y13 protein levels between WT and P2Y1-/- lumbar DRG (n of 4/genotype; p < 0.97).