Expression of G proteins in the olfactory receptor neurons of the newt Cynops pyrrhogaster: Their unique projection into the olfactory bulbs

Abstract

We analyzed the expression of G protein α subunits and the axonal projection into the brain in the olfactory system of the semiaquatic newt Cynops pyrrhogaster by immunostaining with antibodies against Gαolf and Gαo , by in situ hybridization using probes for Gαolf , Gαo , and Gαi2 , and by neuronal tracing with DiI and DiA. The main olfactory epithelium (OE) consists of two parts, the ventral OE and dorsal OE. In the ventral OE, the Gαolf - and Gαo -expressing neurons are located in the apical and basal zone of the OE, respectively. This zonal expression was similar to that of the OE in the middle cavity of the fully aquatic toad Xenopus laevis. However, the Gαolf - and Gαo -expressing neurons in the newt ventral OE project their axons toward the main olfactory bulb (MOB) and the accessory olfactory bulb (AOB), respectively, whereas in Xenopus, the axons of both neurons project solely toward the MOB. In the dorsal OE of the newt, as in the principal cavity of Xenopus, the majority of the neurons express Gαolf and extend their axons into the MOB. In the vomeronasal organ (VNO), the neurons mostly express Gαo . These neurons and quite a few Gαolf -expressing neurons project their axons toward the AOB. This feature is similar to that in the terrestrial toad Bufo japonicus and is different from that in Xenopus, in which VNO neurons express solely Gαo , although their axons invariably project toward the AOB. We discuss the findings in the light of diversification and evolution of the vertebrate olfactory system.

Characterization of glycoconjugates and sialic acid modification in the olfactory bulb of the Chinese fire‐bellied newt (Cynops orientalis)

“…The salamander species investigated in these previous studies commonly exhibited different binding patterns of lectins in the primary projections between the MOB and AOB. These findings suggested the involvement of glycoconjugate heterogeneity in the distinct function of the two olfactory systems, which agrees with the exclusive expression of Gαo in the AOB (Nakada et al, ). In addition, the olfactory glomeruli in the MOB are divided into a subset only in the more terrestrial salamanders (e.g.…”

“…The distribution of olfactory G proteins has been previously reported in the olfactory organ and its primary projection of C. pyrrhogaster (Nakada et al, ). Although the MOB of C. pyrrhogaster receives exclusively axons from Gαolf‐expressing neurons, the AOB receives axons from Gαo‐expressing neurons with a small population of Gαolf‐positive axons.…”

“…The morphology of the receptor neuron and G protein subtype of the Japanese fire‐bellied newt (Cynops pyrrhogaster) is consistent with those in mammals, while Gαolf‐expressing neurons and Gαo‐expressing neurons are intermixed in both the olfactory and vomeronasal epithelia (Nakada et al, ). Gαolf and Gαo proteins are distributed in the axons of receptor neurons and in the termination fields of the olfactory bulb.…”

“…The distribution of olfactory G proteins has been previously reported in the olfactory organ and its primary projection of C. pyrrhogaster (Nakada et al, 2014). Although the MOB of…”

Imorin: a sexual attractiveness pheromone in female red-bellied newts (Cynops pyrrhogaster)

“…This then results in the production of inositol 1,4,5-triphosphate and diacylglycerol, leading to an elevation of intracellular concentrations of Ca 2+ ([Ca 2+ ] i ) and excitation of the receptor cells17181920. We have previously observed that the neurons in the VN organ of the red-bellied newt mostly express Gα o , but that quite a few neurons express Gα olf 21. Therefore, we used a calcium imaging system to test whether imorin could increase [Ca 2+ ] i in dissociated VN cells from male newts.…”