Female Rat Estrous Cycle
day 1--metestrus:
- early: ovarian hormone secretion is relatively low
- late: start of follicular activity
day 2--diestrus:
- follicles continue to develop, see significant increases in estrogen levels
day 3--proestrus:
- early: see further increases in estrogen
- late: estrogen levels peak mid-late proestrus; the rise in estrogen stimulates GnRH and LH surges; the rise in LH will also stimulate preovulatory rise in progesterone
day 4--estrus:
- early: ovulation (resulting from increases in estrogen and LH), and behavioral estrus--proceptive and receptive behaviors (resulting from increases in estrogen and progesterone)
- late: declining levels of estrogen and progesterone
depends on whether female engages in copulation