Portland State University, Department of Biology, 1719 SW 10th Ave, Portland, OR 97206, USA.
Western Oregon University, Department of Biology, 345 N. Monmouth Ave, Monmouth, OR 97361, USA.
Horm Behav. 2021 Feb;128:104893. doi: 10.1016/j.yhbeh.2020.104893. Epub 2020 Dec 24.
Despite the established dichotomy between investment in either reproduction or self-maintenance, a hormonal mechanism that influences an organism's decision to prioritize these behaviors remains elusive. The protein hormone leptin is a likely candidate because it is secreted from adipocytes in proportion to the amount of stored fat in numerous species. Although the majority of studies suggest that leptin stimulates reproduction, the actions of leptin can be context-dependent. Leptin increases sexual behavior in fed individuals, but inhibits sexual behavior in food-restricted individuals. We investigated if exogenous leptin influences sexual behavior in red-sided garter snakes (Thamnophis sirtalis parietalis) experiencing a predictable bout of aphagia during the mating season. We tested two doses of recombinant murine leptin injected for three days. Males were subjected to three mating trials, one on each day of injections, while females were subjected to one mating trial on the last day of injections. Leptin affects male and female snakes similarly by increasing both appetitive (i.e., mating behavior score) and consummatory (i.e., number of copulations, proportion of individuals copulated) sex behavior. We found no evidence to suggest that leptin influenced latency to copulate or duration of copulation. Because leptin promotes reproductive behavior in non-feeding garter snakes, these findings do not align with research on food-restricted mammals. Further investigations into how leptin affects sexual behavior in snakes exposed to food-restriction manipulations would clarify if the role of leptin is evolutionarily divergent.
尽管已经确立了投资于繁殖或自我维持之间的二分法，但影响生物体优先考虑这些行为的激素机制仍然难以捉摸。蛋白激素瘦素是一个可能的候选者，因为它是从多种物种的脂肪储存量成比例地从脂肪细胞中分泌出来的。尽管大多数研究表明瘦素刺激繁殖，但瘦素的作用可能是依赖于环境的。瘦素在进食个体中增加性行为，但在限制食物的个体中抑制性行为。我们研究了外源性瘦素是否会影响交配季节中经历可预测禁食期的红边束带蛇（Thamnophis sirtalis parietalis）的性行为。我们测试了注射三天的两种重组鼠瘦素剂量。雄性接受三次交配试验，每次注射日一次，而雌性在注射的最后一天接受一次交配试验。瘦素通过增加食欲（即交配行为评分）和饱食（即交配次数、交配个体的比例）性行为，对雄性和雌性蛇产生相似的影响。我们没有发现证据表明瘦素影响交配潜伏期或交配持续时间。因为瘦素促进非禁食束带蛇的繁殖行为，这些发现与限制食物的哺乳动物的研究不一致。进一步研究瘦素如何影响暴露于食物限制处理的蛇的性行为，将阐明瘦素的作用是否在进化上有所不同。
