Number of Neurons Expresses Gonadotropin Releasing Hormone in the Hypothalamic Preoptic Area During the Phases of Estrous Cycle of Ewe

In the present study number of neurons that express gonadotropin releasing hormone (GnRH) in the ewe preoptic area (POA) of hypothalamus were compared between the phases of estrous cycle. Hypothalamus of four ewe groups (n=3) of ovariectomized, proestrus, estrus, and luteal were removed after perfusion. The number of GnRH neurons in the POA of four groups was compared, using immunohistochemistry method. GnRH neurons were present in the POA of four groups of ewe. The mean of number of GnRH neurons in estrus ewes was more than ovariectomized ewes. However, there was not significant difference between the numbers of GnRH neurons of POA in three estrous phases. No difference for the number of neurons that express GnRH in the POA of hypothalamus during estrous phases of ewes might indicate that these relatively fixed number cells may perform the estrous cycle control only by control of GnRH release and changing of the secretion of GnRH.