Cellular subtype distribution and developmental regulation of TRPC channel members in the mouse dorsal root ganglion

Transient receptor potential (TRP) channels play essential roles in sensory physiology and their expression in different classes of sensory neurons reflect distinct receptive properties of these neurons. While expression of the TRPV, TRPA, and to a certain degree TRPM classes of channels has been studied in sensory neurons, little is known about the expression and regulation of TRPC channels. In this study we examined the regulation of all TRPC members (TRPC1-C7) throughout embryonic and postnatal development of the dorsal root ganglion (DRG) and nodose ganglion (NG). In adult mice, mRNAs for all channels were present in the DRG, with TRPC1, 3, and 6 being the most abundant, TRPC2, C4, and C5 at lower levels, and TRPC7 at very low levels. While TRPC2 mRNAs were downregulated from high levels at embryonic (E) day 12 and E14 until adult, TRPC4, C5, and C7 expressions increased from E12 to peak levels at E18. TRPC1, C3, and C6, the most abundant TRPC channel mRNAs, increased progressively from E12 to adult. Expression and regulation of TRPC channels mRNAs in the NG were unexpectedly similar to the DRG. TRPC1 and C2 was expressed in the neurofilament-200 (NF-200)-positive large size subclass of neurons, while TRPC3 mRNAs expression, which stained up to 35% of DRG neurons, was almost exclusively present in nonpeptidergic isolectin B4 (IB4)-positive small size neurons that were largely TRPV1-negative. Our results suggest important roles of the TRPC family of channels in sensory physiology of both nociceptive as well as nonnociceptive classes of neurons.