Involvement of Gα_olf‐expressing neurons in the vomeronasal system of Bufo japonicus

Abstract

Most terrestrial vertebrates possess anatomically distinct olfactory organs: the olfactory epithelium (OE) and the vomeronasal organ (VNO). In rodents, olfactory receptors coupled to Gα(olf) are expressed in the OE, whereas vomeronasal receptors type 1 (V1R) and vomeronasal receptors type 2 (V2R), coupled to Gα(i2) and Gα(o) , respectively, are expressed in the VNO. These receptors and G proteins are thought to play important roles in olfactory perception. However, we previously reported that only V2R and Gα(o) expression is detected in the Xenopus laevis VNO. As X. laevis spends its entire life in water, we considered that expression of limited types of chemosensory machinery in the VNO might be due to adaptation of the VNO to aquatic life. Thus, we analyzed the expression of G proteins in the VNO and the accessory olfactory bulb (AOB) of the adult Japanese toad, Bufo japonicus, because this species is well adapted to a terrestrial life. By using immunohistochemical analysis in combination with in situ hybridization and DiI labeling, we found that B. japonicus Gα(olf) and Gα(o) were expressed in the apical and middle-to-basal layer of the vomeronasal neuroepithelium, and that the axons of these Gα(olf) - and Gα(o) -expressing vomeronasal neurons projected to the rostral and caudal accessory olfactory bulb, respectively. These results strongly suggest that both the Gα(olf) - and Gα(o) -mediated signal transduction pathways function in the B. japonicus VNO. The expression of Gα(olf) in the B. japonicus VNO may correlate with the detection of airborne chemical cues and with a terrestrial life.

Expression and cellular localization of the voltage‐gated calcium channel α2δ3 in the rodent retina

“…A mouse monoclonal antibody to Goα (catalog No. MAB3073; EMD Millipore, RRID: AB_94671) detected a single band of 42–43 kDa in homogenates of the olfactory epithelium and the vomeronasal organ in Xenopus laevis and Bufo japonicas (Hagino‐Yamagishi and Nakazawa, ). In the retina, Goα is expressed in rod and cone ON‐type bipolar cells (Haverkamp and Wässle, ; Dhingra et al, ).…”

A putative functional vomeronasal system in anuran tadpoles

“…Gαo‐expressing neurones have been described in the VNO of mammals (Jia & Halpern, ; Halpern & Martinez‐Marcos, ), reptiles (Luo et al., ; Murphy et al., ) and adult amphibians (Hagino‐Yamagishi et al., ; Date‐Ito et al., ; Hagino‐Yamagishi & Nakazawa, ). Moreover, Gαo protein expression was described previously in the VNO of tadpoles of X. laevis and R. arenarum (Hagino‐Yamagishi et al., ; Jungblut et al., ).…”

Existence of Gα<i>_i2</i>-Expressing Axon Terminals in the Goat Main Olfactory Bulb

“…The preparation of goat tissues and the Nissl-stained section of the OB was described by Mogi et al [7]. The immunohistological procedures were described previously [5].…”

“…First, we examined the specificity of the monoclonal mouse anti-Gα i2 (MAB3077; Millipore, Billerica, MA, U.S.A.) and the polyclonal rabbit anti-Gα olf (COP-080058; Cosmo Bio, Tokyo, Japan) with western blotting [5], because these antibodies have not been used in the goat olfactory system. Briefly, cell lysates derived from the olfactory epithelium of the female goats were electrophoresed on an SDS-polyacrylamide gel, and the separated proteins were electroblotted onto transfer membranes.…”

“…As negative controls, the membranes were treated without primary antibodies (Fig. 1, lanes 3 and 6) or with preabsorbing anti-Gα olf , which was prepared by incubating anti-Gα olf with the antigen as described in elsewhere [5] ( Fig. 1, lane 5).…”