Distributions and Variations of sGnRH in Discrete Brain Areas From Common Carp (Cyprinus carpio L.) of Different Ages and Gonadal Conditions

The total content of sGnRH in brain and the regional distributions of sGnRH in discrete brain areas and pituitary were significantly changed with age and gonadal condition.In juvenile fish,the sGnRH was functional inadeguecy,represented by much less total sGnRH content in brain and with no significant distribution variations compared with those of yearling fish.The total content and the regional distributions of sGnRH in discrete brain areas in 3+ year old sexually mature fish were similar to those in yearling sexually mature fish,but the sGnRH content in olfactory bulbs was higher and in pituitary was much lower than that in yearling fish.In yearling fish of different ovarian development,the total content of sGnRH was lower in early stage,highly increased in middle and mature stage,and decreased in regressed stage,showing significant seasonal variations.The contents of sGnRH in discrete brain areas also showed seasonal variations.