Gonadotropin releasing hormone and brooding behavior in the native Thai hen

Changes in the number of hypothalamic gonadotropin releasing hormone-I (GnRH-I) neurons within the Nucleus commissurae pallii (nCPa) were associated with the reproductive cycle of native Thai chickens. In order to further understand the association of GnRH-I in the regulation of brooding behavior in this bird, the native Thai chickens were divided into two groups; chick-rearing (R) and non-chick-rearing (NR) hens. Numbers of visible of GnRH-I-immunoreactive (GnRH-I-ir) neurons in the hypothalamus of R and NR hens were compared utilizing immunohistochemistry. Numbers of visible GnRH-I-ir neurons within the Nucleus anterior medialis hypothalami, Nucleus suprachaiasmaticus, pars medialis, Nucleus septalis lateralis, Nucleus paraventricularis magnocellularis, and Regio lateralis hypothalami areas were observed in both groups, but no differences were seen between R and NR hens. The number of visible GnRH-I neurons in the nCPa was higher (P < 0.05) in the NR than in R hens, and increased in NR hens by day 14 after chick removal. These findings suggest, for the first time, an association of the GnRH system with brooding behavior in continuously breeding birds. Furthermore, the expression of brooding behavior of native Thai chickens might be regulated, in part, by GnRH-I neurons in the nCPa.