L. Forró szerk.: Miscellanea Zoologica Hungarica 7. 1992 (Budapest, 1992)

Gubányi, A., Kéri, Gy. , Fehér, T.; Pekli, J.: A chicken GnRH analogue (Folligen) stimulates plasma testosterone level and sexual activity in the male marsh frog during and out of spawning season - Preliminary notes

GnRH stimulates sexual activity in frogs H5 Discussion Our results demonstrate, that Folligen increased plasma testosterone concentration and induced sexual activity of marsh frogs in different seasons confirming and extending the experimental evidence about GnRH action on sexual steroid production in frogs (cf. McCreery et al. 1982, Pierantoni et al 1984a). To our surprise we found that Folligen (GnRHa) significantly enhanced plasma T levels in frogs tested in summer, without affecting the high plasma estradiol level. Estradiol remained steady at a high level after the Folligen treatment (cf. Polzonetti-Magni et al. 1984). It is difficult for us to interpret these findings since an interruption in the reproductive activity of "green frog complex" has been found during the summer (Polzonetti-Magni et al. 1984), resulting in a transitory refractoriness to environmental cues and causing unresponsiveness of frog testis to GnRH analogue (Buserelin) treatment and pituitary factors (Pierantoni et al 1984b). On the other hand McCreery & Licht (1984) suppose that testicular estradiol can inhibit the LH release, acting as a negative feedback. Taking these results into consideration, Folligen might affect testosterone production of the testis by modifying gonadotropin release of pituitary or by a possible direct gonadal action. In this paper we have shown the stimulatory effect of a new GnRH analogue (Folligen) on plasma testosterone level and breeding behaviour of marsh frogs. The results of summer experiments with Folligen proved that this hormone is suitable for inducing sexual activity of frogs in the postreproductive phase, too. In conclusion, also taking into account previous investigations with Folligen (Kéri et al. 1990, Gubányi et al. 1991), this chicken I GnRH analogue is very effective in stimulating reproductive functions in frogs and different classes of vertebrates. References Bodrogi, L. & Fehér, T. (1980): Radioimmunological method for determination of testosterone in human blood, amniotic fluid and tissue. - Izotóptechnika 23: 175-181. Cariello, L., Romano, L., Spagnuolo, A., Zanetti, L., Fasano, S., Minucci, S., Di Matteo, L., Pierantoni, R. & Chieffi, T. (1989): Molecular forms of immunoreactive gonadotropin-releasing hormone in hypothalamus and testis of the frog, Rana esculenta - Gen. Comp. Endocrinol. 75: 343-348. Fasano, S., Minucci, S., Di Matteo, L., D'Antonio, M. & Pierantoni, R. (1989): Intratesticular feedback mechanisms in the regulation of steroid profiles in the frog, Rana esculenta - Gen. Comp. Endocrinol. 75: 335-342. Fasano,S., Minucci, S., Pierantoni, R., Fasolo, A., Di Matteo, L., Basile, C, Varriale, B. & Chieffi, G. (1988): Hypothalamus-hypophysis and testicular GnRH control of gonadal activity in the frog, Rana esculenta: Seasonal GnRH profiles and annual variations of in vitro androgen output by pituitary-stimulated testis - Gen. Comp. Endocrinol. 70: 31-40. Gubányi, A., Havassy, L., Kéri, Gy. & Pekli, J. (1991): Effect of cGnrH and different GnRH analogs on breeding behaviour of water frogs (Rana esculenta complex, Anura, Ranidae) - In: Korsós, Z. & Kiss, I. (eds): Proc. Sixth. Ord. Gen. Meet. S. E. H., Budapest 1991, (in press). Kéri. Gy., Gulyás, T, Horváth, A., Szőke, B., Bökönyi, Gy. & Teplán, I. (1990): Synthesis and characterization of a novel GnRH analog which stimulates reproductive functions in fishes and mammals -Pep.Res. 3: 142-147. King, A. J., Mehl, A. E. I., Tyndale-Biscoe, H. C, Hinds, L. & Millar, R. (1989): A second form of gonadotropin-releasing hormone (GnRH), with Chicken GnRH Il-like properties, occurs together with mammalian GnRH in marsupial brains - Endocrinology 125(5): 2244-2252. Licht,P, Millar, R. P., King, J. A, McCreery, B. R., Mendoca, M. T., Bona-Gallo, A. & Lofts, B. (1984): Effects of chicken and mammalian gonadotropin-releasing hormones(GnRH) on in vitro pituitary gonadotropin release in amphibians and reptiles - Gen. Comp. Endocrinol. 54: 89-96.