Endocrine regulation of reproductive behavior in the newt Cynops pyrrhogaster

Hormonal control of the expression of courtship behavior and of secretion of the female-attracting pheromone sodefrin by the male red-bellied newt, Cynops pyrrhogaster, together with the hormonal influence on the responsiveness to the pheromone in the female, is reviewed.Expression of the initial stage of the courtship behavior, i.e., tail vibration by the male in front of the female, is dependent on prolactin (PRL) and androgen. During the courtship, sodefrin seems to be released from the cloaca through the ducts of the abdominal gland. Both content of immunoreactive sodefrin and preprosodefrin mRNA levels in the abdominal gland are elevated by a combination of PRL and androgen, indicating that the pheromone synthesis is stimulated by these two hormones. On the other hand, the discharge of sodefrin is accelerated by AVT, its action being mediated by V1 receptor. In female newts, responsiveness of the vomeronasal epithelium to the pheromone is elevated by a combination of PRL and estrogen. Thus, it can be concluded that PRL, AVT, and sex steroids are key hormones for the reproductive performance in the red-bellied newt. In this article, the significance of the structure of the pheromone molecule as a peptide is also discussed in terms of its species-specificity and its effectiveness in an aquatic environment.