Department of Psychology, University of California, Berkeley, 2121 Berkeley Way West, Berkeley, CA, 94720, USA.
Department of Integrative Biology, University of California, Berkeley, 3040 VLSB, Berkeley, CA, 94720, USA.
Biol Sex Differ. 2023 Sep 4;14(1):55. doi: 10.1186/s13293-023-00542-7.
The rat estrous cycle first characterized by Long and Evans in 1922 profoundly affected the course of endocrine research. Investigators took advantage of sex steroid hormone fluctuations associated with the cycle to assess hormonal influences on anxiety, depression, food intake, stress, brain structure and other traits. Similarities of the rat estrous and human menstrual cycles facilitated understanding of human reproductive physiology. I assessed the impact of awareness of the estrous cycle on the emergence of a sex bias that excluded female rats from biomedical research.
Beginning with the 1918 volume of the American Journal of Physiology and ending in 1976 when the journal subdivided into several separate disciplinary journals, all studies conducted on rats were downloaded; the use of females, males, both sexes and sex left unspecified was tabulated for 485 articles. A second analysis tracked the number of rat estrous cycle studies across all disciplines listed in PubMed from 1950 to 2021.
The description and awareness of variability associated with the rat estrous cycle was correlated with a precipitous decline in investigations that incorporated both sexes, a marked increase in male-only studies and a striking sex bias that excluded female rats. The number of rat estrous cycles studies increased markedly from earlier decades to a peak in 2021.
The initial description the rat estrous cycle was correlated with a substantial decline in investigations that incorporated both sexes; one result was a marked increase in male-only studies and a striking sex bias that excluded female rats from biomedical research. Recognition of the advantages of studies that incorporate the rat estrous cycle has resulted in recent years in an increase of such investigations. Female rats and females of several other species are not more variable than their male counterparts across traits, arguing for female inclusion without requiring cycle monitoring. There, remain, however, many advantages of incorporating the estrous cycle in contemporary research.
1922 年，朗(Long)和埃文斯(Evans)首次对大鼠发情周期进行了描述，这对内分泌研究产生了深远的影响。研究人员利用与周期相关的性激素波动来评估激素对焦虑、抑郁、食物摄入、压力、大脑结构和其他特征的影响。大鼠发情周期与人类月经周期的相似之处促进了对人类生殖生理学的理解。我评估了对发情周期的认识对出现性别偏见的影响，这种偏见将雌性大鼠排除在生物医学研究之外。
从 1918 卷的《美国生理学杂志》开始，到 1976 年该杂志细分为几个独立的学科期刊结束，所有在大鼠身上进行的研究都被下载；对于 485 篇文章，记录了使用雌性、雄性、雌雄两性和未说明性别的情况。第二项分析追踪了从 1950 年到 2021 年在 PubMed 列出的所有学科中大鼠发情周期研究的数量。
对大鼠发情周期相关变异性的描述和认识与包含雌雄两性的研究急剧减少相关，雄性单独研究的数量显著增加，并且存在明显的性别偏见，将雌性大鼠排除在生物医学研究之外。大鼠发情周期研究的数量从早期几十年显著增加到 2021 年的峰值。
大鼠发情周期的最初描述与包含雌雄两性的研究数量的大幅减少相关；其结果之一是雄性单独研究的数量显著增加，并且存在明显的性别偏见，将雌性大鼠排除在生物医学研究之外。近年来，由于认识到包含大鼠发情周期的研究的优势，此类研究的数量有所增加。在多个特征上，雌性大鼠和其他几种物种的雌性并不比其雄性对应物更具变异性，因此不需要进行周期监测即可纳入雌性。然而，在当代研究中仍然存在许多包含发情周期的优势。
