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
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 bv A. Gubányi, Gy. Kéri, T. Fehér and J. Pekli (Received June 15,1992) Abstract: The stimulatory effect of a new analogue of chicken I. gonadotropin-releasing hormone (Folligen) has been studied on specimens of marsh frog, Rana ridibunda. Folligen increased plasma testosterone (T) levels and induced breeding behaviour both during and out of the spawning season. Folligen (GnRHa) significantly enhanced plasma T levels in frogs tested in summer, and estradiol remained steady at high levels after the Folligen treatment. At the same time this hormone induced sexual activity of frogs in the postreproductive phase, too. According to our current and previous results, Folligen is suitable for stimulation of reproductive functions in lower classes of vertebrates. Key words: Rana ridibunda, GnRHa, Folligen. sexual activity, testosterone Introduction Since the discovery of the porcine gonadotropin-releasing hormone structure four more molecular forms of GnRH have been isolated and characterised from vertebrate brains: chicken I, chicken II, salmon and lamprey forms (see King et al. 1989 for review). Two molecular forms of GnRHs have been identified in the brain of green frogs (Rana esculenta complex), these forms are closely related to salmon and chicken II. GnRHs (Cariello et al. 1989). Recently, the GnRH analogue (GnRHa), Buserelin [ D .Ser(But) 6 desGly 10 ]-GnRH-ethylamide, has been used for studying the action of GnRH on the reproductive process (Pierantoni et al. 1984a, Fasano et al. 1988) in these species. GnRH and its agonists can enhance the testicular function of frogs, either by stimulating the release of gonadotropins from the anterior pituitary (McCreery et al. 1982, Licht et al. 1984), or by directly enhancing the testicular androgen production (McCreery et al. 1982, Pierantoni et al. 1984a, Pierantoni et al. 1984b). Temperature and photoperiod also play an important role in the reproductive process, regulating androgen levels of male green frogs, Rana esculenta, through the central nervous system (Rastogi et al. 1978). Seasonal changes are well established in plasma steroid levels of green frogs in the natural environment (Polzonetti-Magni et al. 1984, Varriale et al. 1986). Testosterone (T) and dihydrotestosterone (DHT) showed annual fluctuation in the plasma. Testosterone increased significantly in January, and peaked in February and early March. DHT peaked in May-June, and a decrease could be found thereafter (Fasano et al. 1989). However, plasma estradiol peaked only in May (Varriale et al. 1986). Comparatively high estradiol levels were observed in male and female Rana esculenta specimens by Polzonetti-Magni et al. (1984) in May-July, and they suggested that
