Troconis Eileen L, Seo Changwoo, Guru Akash, Warden Melissa R
Department of Biological and Biomedical Sciences, Cornell University, Ithaca, NY 14853 USA.
Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853 USA.
bioRxiv. 2023 Aug 19:2023.05.14.540716. doi: 10.1101/2023.05.14.540716.
Sexual stimulation triggers changes in female physiology and behavior, including sexual satiety and preparing the uterus for pregnancy. Serotonin is an important regulator of reproductive physiology and sexual receptivity, but the relationship between sexual stimulation and serotonin neural activity in females is poorly understood. Here, we investigated dorsal raphe serotonin neural activity in females during sexual behavior. We found that serotonin neural activity in mating females peaked specifically upon male ejaculation, and remained elevated above baseline until disengagement. Artificial intravaginal mechanical stimulation was sufficient to elicit increased 5-HT neural activity but the delivery of ejaculatory fluids was not. Distal penis erectile enlargement ("penile cupping") at ejaculation and forceful expulsion of ejaculatory fluid each provided sufficient mechanical stimulation to elicit serotonin neuron activation. Our study identifies a female ejaculation-specific signal in a major neuromodulatory system and shows that intravaginal mechanosensory stimulation is necessary and sufficient to drive this signal.
性刺激会引发雌性生理和行为的变化，包括性满足感以及使子宫为妊娠做好准备。血清素是生殖生理和性接受能力的重要调节因子，但雌性中，性刺激与血清素神经活动之间的关系却鲜为人知。在此，我们研究了性行为期间雌性中缝背核血清素神经活动。我们发现，交配雌性中的血清素神经活动在雄性射精时达到峰值，并在脱离接触前一直高于基线水平。人工阴道机械刺激足以引发5-羟色胺神经活动增加，但射精液的注入却没有这种效果。射精时阴茎远端勃起增大（“阴茎套叠”）以及射精液的强力排出均提供了足够的机械刺激，以引发血清素神经元激活。我们的研究在一个主要的神经调节系统中识别出了一种雌性射精特异性信号，并表明阴道内机械感觉刺激是驱动该信号的必要且充分条件。
