Abstract
The dose and temporal effects of oestrogen and progesterone treatment on the induction of receptivity in female Mongolian gerbils were investigated. One group of animals was primed with 10 μg oestradiol benzoate (OB) 48 and 24 h prior to testing and received 500 μg progesterone (Pr) 0, 1, 2, 3, 6, 9, 12, 15, 18, 21 or 24 h prior to testing. These subjects were found to exhibit high levels of receptivity from hour 2 to hour 18. This is similar to the reported duration of heat during natural oestrus. A second group of animals were primed with 10 μg OB and were then given either 0, 10, 50, 100, 250 or 500 μg Pr 3 h prior to testing. Results indicated that the administration of 100 μg Pr could elicit high levels of receptivity. A final group of animals were given either 0·5, 1·0, 5·0 or 10·0 μg OB 48 and 24 h before testing and then 100 μg Pr 3 h prior to testing. It was found that only the 10 μg dose of OB elicited high levels of receptivity in these animals.