G protein alpha subunits in the olfactory epithelium of the holocephalan fish Chimaera monstrosa.

Receptor neurons in the olfactory and vomeronasal epithelia of vertebrates have dendritic specialization that is correlated to the receptor gene family they express and the G protein coupled with that receptor (in particular the G protein alpha subunit). There are not very many data in the literature about the morphological and molecular features of the olfactory epithelium of Chondrichthyes. In this work, the presence and distribution of different types of G protein alpha subunits (Galpha(o), Galpha(q) and Galpha(olf)) were investigated in the olfactory epithelium of the holocephalan Chimaera monstrosa using immunohistochemistry. Only Galpha(o)-like immunoreactivity was detected in the microvillous receptor neurons and in numerous axon bundles of the fila olfactoria. These preliminary data are in agreement with studies showing G protein alpha subunits in elasmobranchs and support the data present in the literature about putative odorant receptor families in the sequenced genome of the holocephalan Callorhinchus milii.