Hormonal influence on the olfactory response to a female-attracting pheromone, sodefrin, in the newt, Cynops pyrrhogaster

Sodefrin is a female-attracting pheromone isolated from the abdominal glands of male newts, Cynops pyrrhogaster. Previously, the preference of conspecific female newts for sodefrin was shown to be completely abolished by plugging the bilateral nostrils, indicating that it acts on the olfactory organ. To determine the sensitivity of the olfactory receptor cells to sodefrin, electro-olfactograms (EOGs) in response to sodefrin solution were recorded from the ventral nasal epithelium of sexually developed female newts. Sodefrin elicited marked EOG responses in a dose-dependent manner on the epithelium of the lateral nasal sinus (LNS) region, a putative vomeronasal organ. In ovariectomized females, treatment with prolactin (PRL) and estrogen markedly enhanced the EOG response to sodefrin. The EOG response to the pheromone was also enhanced considerably by treatment with either PRL or estrogen alone. A slight but significant elevation was observed in castrated males receiving PRL plus estrogen or estrogen alone. It was concluded that the main site of action of sodefrin resides in the lateral sinus region and that sensitivity to sodefrin is under the control of PRL and estrogen. The presence of a sex difference in olfactory sensitivity to the hormones and/or pheromone was also suggested.