RT journal article T1 Characterization of the estrous cycle in the Amazon spiny rat (Proechimys guyannensis) A1 Sanabria, Viviam A1 Bittencourt, Simone A1 Rosa Macías, Tomás de la A1 Livramento, Jomenica A1 Tengan, Celia A1 Scorza, Carla A A1 Cavalheiro, Esper A1 Amado, Debora A2 Neurociencias K1 Ecology K1 Endocrinology K1 Proechimys guyannensis K1 Estradiol K1 Hormones AB Males of Proechimys guyannensis, a rodent living in the Amazon rainforest are studied in biomedical research because of their antiepileptogenic mechanism. Females are usually taken from experimental designs, because of limited data of this sex. This study aimed to characterize the estrous cycle to include females together with males in research in a more balanced approach. The estrous cycle of P. guyannensis based through exfoliative cytology, determination of the vaginal occlusion membrane state, and hormonal analysis. In this study, cytological analyses of vaginal smears were performed for three months, three times a day. The observed length of the estrous cycle was 247 ± 81 h (mean ± SD) with a reproductive phase of 27.08 ± 17.39 h (estrus stage). We observed a frequent presence of both the open and closed states of the vaginal membrane in the estrus stage (fertile period) although only the open stage is a prerequisite for successful copulation. High levels of progesterone and estradiol were detected in proestrus. Levels of follicle-stimulating hormone peaked at the estrus stage. These data will establish the parameters and subsidies to set the grounds for future research either for investigating the biology of this species or to use P. guyannensis in research that previously excluded females. Information regarding female Proechimys is relevant to not only describe the species but also explain the interaction between sex hormones and physiological responses. Moreover, the present results will enhance rigor and reproducibility in preclinical studies. In conclusion, P. guyannensis reproductive cycles can occur spontaneously and cyclically independent of mating stimulation and the high levels of FSH in the estrus stage, suggest that ovulation occurs in the late phase of the estrus. PB CellPress SN 2405-8440 YR 2019 FD 2019-12 LK http://hdl.handle.net/10498/34498 UL http://hdl.handle.net/10498/34498 LA eng NO This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001, supported as well by AFIP and by grants from Fapesp, CNPq, and PAEC OEA - GCUB. DS Repositorio Institucional de la Universidad de Cádiz RD 10-may-2026