Seasonal changes in hypothalamic gonadotropin inhibitory hormone expression in the paraventricular nucleus of chukar partridge (Alectoris chukar)

Gonadotropin inhibitory hormone (GnIH) as a hypothalamic neuropeptide inhibits the synthesis and release of gonadotropins via affecting gonadotropin releasing hormone (GnRH) neurons and could be a key neuropeptide in regulating seasonal breeding in birds. The aim of the present study was to investigate the expression of GnIH in the hypothalamus of male and female chukar partridges (Alectoris chukar) during the breeding and non-breeding seasons. In breeding (May) and non-breeding (January) seasons, the brains of sexually-matured male (n = 10) and female (n = 10) chukar partridges were removed following fixation. Sections (30 μm) were prepared from the entire diencephalon and stained immunohistochemically. GnIH-immunoreactive neurons were primarily found in paraventricular nucleus, and few positive neurons were detected in dorsomedial nucleus. The numbers f GnIH-immunoreactive neurons were significantly lower in the breeding season compared with the non-breeding soeason in both male and female (P < 0.05). There were no significant differences in the number of GnIH neurons in paraventricular nucleus between the sexes. Gonadal weight and volume in male and female partridges were significantly higher in the breeding season. The results showed that GnIH neurons may partly contribute to the regulation of the seasonal breeding in the chukar partridge.