Neuroendocrine Control of the Ovarian Cycle of the Rat

This chapter discusses the control of the ovarian cycle of the rats by the brain and its interaction with the anterior pituitary gland and ovaries. The ovarian cycle of the rats is characterized by a brief luteal phase, and the events of the cycle are largely under photoperiodic control. That is, the lighting periodicity plays a dominant role in the incidence and duration of the stages of the ovarian cycle. During the estrous cycle of the rat, three or more generations of corpora lutea can be present on the ovary from the immediately preceding ovulatory cycles whereas the preovulatory period of the estrous cycle is characterized by a growth of ovarian follicles and a concomitant enhanced secretion of estrogen. The secretion rate of estradiol into ovarian venous plasma is low on estrus, begins to rise significantly by late on metestrus through the morning of diestrus, and reaches peak concentrations by the afternoon of proestrus.