Contribution of Chicken GnRH-II and Lamprey GnRH-III on Gonadotropin Secretion

Proper gonadal function in mammals depends on gonadotropins secreted from the pituitary gland in a pulsatile manner. The hypothalamus, in turn, controls the secretion of gonadotropins by the pulsatile secretion of gonadotropin releasing hormone (GnRH) into the portal circulation of the pituitary. The idea of brain control over the hypophysis was first postulated by Geoffrey Harris during the late 1940s and early 1950s (Harris, 1948). The evidence available at that time indicated that stimulation of the central nervous system, but not direct stimulation of the pars distalis or neural lobe, caused the release of adenohypophysial hormones. During the 1950s and 1960s, trophic substances were extracted from the brain of different species (Guillemin, 2005). These releasing factors obtained from the median eminence affected secretions of the pars distalis. The search for these releasing factors was lead by McCann, Schally and Guillemin (Guillemin and Rosenberg, 1955; McCann and Fruit, 1957; Rumsfeld and Porter, 1962; Saffran et al., 1955).