Immunohistochemical co-expression of carbonic anhydrase II with Kv1.4 and TRPV1 in rat small-diameter trigeminal ganglion neurons

The co-expression of carbonic anhydrase II (CAII) with the voltage-gated potassium channel subtype 1.4 (Kv1.4) or the vanilloid receptor (TRPV1) was examined in adult rat trigeminal ganglion (TG) neurons by using the immunofluorescence method. The small-diameter Kv.1.4-positive TG neurons co-expressed CAII immunoreactivity (47%). Most TRPV1-positive TG neurons (79%) had the CAII immunoreactivity, but showed a lack of immunoreactivity for a neurofilament protein (NF200), a maker of large TG neurons with myelinated axons. The fact that CAII-immunoreactive TG neurons revealed a common expression of both Kv1.4 and TRPV1 leads us to suggest that CAII may be one of the nociceptive neuronal markers.