In the present study, we have used in situ hybridisation to examine the distribution of calcium channel subunits in rat dorsal root ganglion (DRG) neurons. Within DRG neurons, the calcium channel alpha subunit mRNAs alpha(1A), alpha(1B), alpha(1C), alpha(1D), alpha(1E), alpha(1I) and alpha(1S) were readily detected in small (<25 microm), medium (25-45 microm) and large (>45 microm) diameter neurons. alpha(1F) was present at very low levels in these neurons whilst alpha(1G) was virtually undetectable. The calcium channel auxiliary subunits alpha(2)delta(1) and alpha(2)delta(2) showed a complementary pattern of distribution to that of alpha(2)delta(3) in DRG neurons. alpha(2)delta(1) and alpha(2)delta(2) transcripts were expressed predominantly in small c-type sensory neurons and were present at lower levels in large Abeta-type sensory neurons. In contrast, alpha(2)delta(3) mRNA was present in high quantities in the large-diameter cells but was expressed at lower levels in small-diameter neurons of the DRG. The present study provides an insight into the molecular profile of calcium channel alpha(1) and alpha(2)delta subunits in the neurons responsible for transmitting sensory information.