Because hormonal fluctuations occur in all women, yet not all women experience clinical depression, it's likely that women who develop hormone-related depression and mood disorders have a genetic predisposition to them, Steiner adds. Further research is needed, he says, to identify the specific genetic markers that might lead to a better understanding of how the balance between estrogen, progesterone, testosterone, and other reproductive hormones affects brain function and increases women's susceptibility to depression.
In recent animal studies, Rebecca Craft, PhD, and her colleagues at Washington State University have found that differences in sensitivity to pain and opiate analgesia between males and females may be due primarily to testosterone exposure during early development. Using a rat model that exhibits particularly dramatic sex differences in response to opiate analgesia, the researchers manipulated hormones in rats when the animals were very young and then again when the rats were adults. The animals' pain thresholds and their response to morphine-induced analgesia were then evaluated using two different tests.
Craft and her colleagues found that early testosterone deprivation increased pain sensitivity in males, making them more like "normal" females. Surprisingly, this effect could be reversed with only two weeks of testosterone treatment during adulthood. Females given testosterone as neonates showed different pain thresholds than untreated females--in other words, they became more like "normal" males. Unlike with the male rats, however, giving the female rats testosterone supplements in adulthood had no further effect.
"These results suggest that differential pain sensitivity in adult male rats compared to females is primarily due to testosterone exposure during development," says Craft.
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Contact: Leah Ariniello
dawn@sfn.org
202-462-6688
Society for Neuroscience
24-Oct-2004