SEX AND REPRODUCTIVE STATUS RELATED BRAIN CONTENT OF MAMMALIAN AND CHICKEN-II GNRHS IN RANA-ESCULENTA

Mammalian and chicken-II forms of gonadotropin-releasing hormone (mGnR H and cGnRH-II, respectively) have been measured simultaneously in the brain, pituitary, and peripheral terminal nerves (nasal area tissue) of adult males and females of a representative amphibian, Rana esculen ta, during the annual reproductive cycle, Whereas in the male, brain c oncentrations of both GnRH forms showed significant reproductive statu s-related fluctuations, in the female brain only cGnRH-II content show ed significant changes. The highest GnRH levels were recorded just pri or to breeding in both sexes, In the pituitary both GnRHs were present in all seasons, In the peripheral terminal nerves, instead, only mGnR H was detected in all seasons confirming our previous immunohistochemi cal data, In both sexes furthermore, the brain and pituitary mGnRH lev els were consistently much higher than those of cGnRH-II and there wer e no sex-related differences in the brain and pituitary content of GnR Hs. Seasonal changes in brain GnRH levels may correlate with plasma se x steroid levels reinforcing the postulate that sex steroids affect Gn RH neuronal systems.