RFRP-ir cell numbers are reduced during the LH surge and reinstated thereafter. A, Low-power photomicrograph of RFRP-ir cell body labeling in the DMH on the day of diestrus; B and C, low-power photomicrographs of RFRP-ir cell body labeling in the DMH on the day of proestrus during the trough (1800 h) and peak (2300 h) of expression, respectively; D, mean (±sem) RFRP-ir cell counts on the day of diestrus and throughout the day of proestrus. *, Significantly different from diestrous values and 2300-h values on the day of proestrus, P < 0.05.