抄録
This study was conducted to examine whether or not the post-luteinizing hormone (LH) surge termination of estrus could be delayed by prolonged exposure to estradiol. Subcutaneous tubings containing estradiol were implanted in eight ovariectomized goats to maintain blood estradiol at the follicular phase level for 56-80 h. Behavior observation and blood sampling were carried out every 2 h for 114 h from 6 h before through 108 h after the initiation of estradiol treatment. As a result, the duration of proceptivity (defined as an active approach to the male) and receptivity (defined as an acceptance of the male) were extended in the manner reflecting the length of estradiol administration. The proceptivity and receptivity disappeared at 14.5 ± 5.0 h and 8.0 ± 3.6 h (mean ± SEM, n=8) after the removal of estradiol tubings, respectively. These results suggest that the termination of estrus in female goat is due to a decline of circulating estradiol level following the LH surge, and that the central nervous system regulating behavioral estrus maintains its responsiveness to estradiol even at the post-LH surge period.
