Effects of Gonadotrophin-Releasing Hormone Variants on Reproductive Organs and Plasma Testosterone in the Male Lizard, Podarcis s. sicula

The effects of various gonadotrophin-releasing hormone (GnRH) forms (mammalian GnRH (mGnRH), chicken I GnRH (cGnRH-I), chicken II GnRH (cGnRH-II) and salmon GnRH (sGnRH)) on the genital apparatus and plasma testosterone level in the male lizard, Podarcis s. sicula , have been investigated.
In short duration experiments (20 min to 76 h) GnRH forms did not affect testicular and epididymal morphology. A single dose (0.05 μg) of mGnRH, cGnRH-II and sGnRH, however, induced a rise in plasma testosterone after 20 to 40 min. Variable results were obtained in the animals given GnRH variants every 12 h for 3 days since mGnRH and cGnRH-I caused a decrease of circulating hormone; cGnRH-II and sGnRH a slight increase.
Daily peptide administration, for 15 to 30 days, caused severe inhibition of both testicular and epididymal activity and a significant drop of circulating testosterone.
In Podarcis s. sicula , species specificity of pituitary sensitivity to GnRH variants appeared to be low. On the other hand, this gland seemed to show some desensitization after chronic peptide administration.