Localization of Receptors for Sex Steroids and Pituitary Hormones in the Female Genital Duct throughout the Reproductive Cycle of a Viviparous Gymnophiona Amphibian, Typhlonectes compressicauda

SIMPLE SUMMARY: Females of the legless amphibian Cayenne caecilian Typhloneces compressicauda demonstrate a biennial viviparous reproductive cycle, with complex morphological alterations in its oviduct. During the first year, these morphological variations permit the capture of the oocytes at ovulation and the pregnancy in the posterior part transformed into uterus. Pregnancy lasts 6 to 7 months and, at parturition, the female gives birth to 6 to 8 newborns which look like small adults.The second year of the cycle is a sexual rest period, allowing females to replenish their body reserves. The hormonal receptors detected in the different cell types of the oviduct confirm that the cyclical development of the genital tract is dependent on sex and pituitary hormones, with a direct control by the pituitary gland. ABSTRACT: Reproduction in vertebrates is controlled by the hypothalamo-pituitary-gonadal axis, and both the sex steroid and pituitary hormones play a pivotal role in the regulation of the physiology of the oviduct and events occurring within the oviduct. Their hormonal actions are mediated through interaction with specific receptors. Our aim was to locate α and β estrogen receptors, progesterone receptors, gonadotropin and prolactin receptors in the tissues of the oviduct of Typhlonectes compressicauda (Amphibia, Gymnophiona), in order to study the correlation between the morphological changes of the genital tract and the ovarian cycle. Immunohistochemical methods were used. We observed that sex steroids and pituitary hormones were involved in the morpho-functional regulation of oviduct, and that their cellular detection was dependent on the period of the reproductive cycle.