Progesterone treatment is not necessary for sexual experience-enhanced paced mating behavior in estradiol...

Sexual behavior in female rats varies depending on sexual history and the combination of ovarian hormones administered to induce receptivity. Experiment 1 tested whether paced mating behavior differed in sexually experienced rats when receptivity was induced with sequential estradiol benzoate (EB) and progesterone (P) or EB-Alone. Rats gained paced mating experience under EB/P (10 μg EB 48 hr + 1 mg P 4-6 hr before mating) and then were primed with EB-Alone (2 μg EB for 6 days). Rats primed with EB-Alone were fully receptive but returned to the male more slowly, spent less time with the male, had longer interintromission intervals, showed fewer proceptive behaviors and more rejection behaviors, and had significantly longer test durations compared to when rats were primed with EB/P. Experiment 2 tested whether sexual experience-induced changes to paced mating behavior occur under both EB/P and EB-Alone hormone priming regimens. Rats received EB/P or EB-Alone prior to four paced mating tests. With sexual experience under either hormone regimen, rats showed shorter contact-return latencies to intromission, shorter interintromission intervals, and more proceptive behaviors. However, relative to EB/P-primed rats, EB-Alone-primed rats exited the male compartment more frequently after mounts and intromissions, spent less time with the male, had longer interintromission intervals, displayed fewer proceptive behaviors and more rejection behaviors, and had longer test durations, indicating lower sexual motivation. Collectively, these data illustrate that experience-enhanced paced mating behavior occurs with either EB/P or EB-Alone priming, but progesterone further facilitates mating behavior. (PsycInfo Database Record (c) 2025 APA, all rights reserved).