[The effect of melatonin and prolactin on secretory activity of hypothalamo-pituituary GnRh-LH system in sheeps]

brain brebis central nervous system cerebro ciclo estral control hormonal contrôle hormonal cycle oestral encéphale ewes gnrh gonadotrophine gonadotropinas gonadotropins hormonal control hormonas hormonas pituitarias hormone hormone hypophysaire hormones lh melatonin melatonina methods mélatonine méthode métodos oestrous cycle oveja ovin ovinos pituitary hormones prolactin prolactina prolactine reproducción reproduction secreción secretion sheep sistema nervioso central système nerveux central sécrétion