Immunocytochemical study of G(i)2alpha and G(o)alpha on the epithelium surface of the rat vomeronasal organ

To investigate in detail the distribution of G protein subtypes G(i)2alpha and G(o)alpha along the surface of the vomeronasal epithelium, we used double labeling immunocytochemical methods and electron microscopy. We examined the immunoreactivity of these surface structures with antibodies against G(i)2alpha and G(o)alpha. G(i)2alpha- and G(o)alpha-positive cells were observed at the epithelial surface and were evenly distributed. Electron microscopy revealed that strong immunoreactivities to both antibodies were observed on the microvilli and knob-like surface structures of receptor cells. No immunoreactivity was found on the microvilli or surface membranes of supporting cells. This expression pattern is similar to that reported for putative pheromone receptors. These data confirm that there are two distinct classes of vomeronasal receptor cells expressed at the surface of the epithelium. These two classes of receptors correspond to the same G(i)2alpha- and G(o)alpha-positive cells distributed in cell body layers of the epithelium and in the axon terminals in the accessory olfactory bulb.