10/12/2023 0 Comments Download free the lab rats![]() ![]() “Normal” levels of testosterone in healthy men can range from 215 nanograms per deciliter to four times that amount, and can spike around times of sex or exercise. “If we’re arguing estrogens are important, androgens are important too, and highly sensitive,” Spritzer says. Testosterone, a type of hormone called an androgen, “can vary 10-fold over the lifetime of a rat,” says Mark Spritzer, a behavioral neuroendocrinologist at Middlebury College in Vermont. Even male rats housed near female rats will have higher testosterone levels than male rats living a monastic life. Let him mate with a female, and his testosterone spikes. ![]() Males, whether of mice or men, are hardly paragons of hormonal stability, the evidence suggests.Ī male rat bullying another will show a testosterone rise. So the scientists thought, why risk it? Better to just study males. With behavioral differences clearly linked to the reproductive cycle, scientists quickly came to believe that the cycle “was the primary thing that would drive your data,” Shansky says. Female rats, for example, will self-administer more cocaine during estrous than at other times, and show less anxiety-like behavior immediately before estrous. Estrogen or progesterone levels on one day could be up to four times as much as on the day before. In rodents, that cycle is compressed to four or five days. In humans, reproductive hormones such as estrogen and progesterone ebb and flow over a roughly 28-day cycle. ![]()
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