Hormonal and pheromonal control of reproduction

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Hormonal and pheromonal control of reproduction was investigated focusing on the hormones and pheromones involved in the expression of reproductive behavior in the newt, Cynopus pyrrhogaster. During the breeding season, the male newt exhibit a specific courtship behavior; vibration of the tail in front of the female partner discharge of a female-attracting pheromone (sodefrin) and deposition of spermatophores. The tail vibration was revealed to be induced by prolactin (PRL) and androgen. The expression of this behavior was enhanced by arginine vasotocin (AVT) via V la receptor. In this case, PRL and AVT were evidenced to act centrally. In the case of PRL, the site of action was postulated to be neurons situated in the preoptic recess organ and / or nucleus infundibularis dorsalis where immunoreactive PRL receptors are abundant AVT also induced the discharge of both sodefrin and spermatophore presumably by acting peripherally. Synthesis of sodefrin precursor protein in the abdominal gland of the cloaca was considered to be enhanced by PRL and androgen since sodefrin precursor mRNA levels were elevated by PRL and androgen. Responsiyeness of the vomeronasal epithelium of the female newt to sodefrin was also revealed to be under the control of PRL and estrogen as judged from electroolfactogram response. Sodefrin-precursor-like protein cDNA was obtained from a cDNA library of C. ensicauda abdominal gland. According to the deduced amino acid sequence of the protein, sodefrin-like pheromone of C. ensicauda was considered to be decapeptide with a substitution of two amino acid residues. This putative pheromone was isolated from the abdominal gland of C. ensicauda and presence of its bioactivity was confirmed. The pheromone, designated silefrin, was effective only on the conspesific female, as in the case of sodefrin, suggesting the newt pheromones are species-specifia.