Hormone levels and behavior
It is difficult to determine how hormones affect the psyche of women in the various stages of menstruation. American scientists have now examined the brains of female rats to see how they are influenced by sex hormones. They describe how changing estrogen levels alter cognitive function and perhaps even emotions. G. B. Karkanias and his colleagues from the Albert Einstein College of Medicine in New York investigated the influence of the female sex hormone estradiol on the number of hormone receptors in the nervous system (December issue of Neuroscience). The reaction to nerve impulses depends on their existence. If there are no receptors, the signal goes unnoticed, while a larger number of receptors means that a signal is transmitted strongly and possibly also leads to a violent reaction.
In their experiment, the scientists used female rats that no longer had any ovaries and therefore did not produce any estradiol themselves. A portion of these rats were given a 48-hour dose of estradiol. After 48 hours, the researchers found that the estradiol-treated rats had fewer norepinephrine receptors in their brains than the control group.
Karkanias claims that the reduced number of receptors suggests that estradiol also affects non-reproductive brain functions controlled by norepinephrine. He says that this type of receptor - the alpha-adrenergic receptors - also affects cognitive functions such as thinking, remembering, learning and planning.
It is thought likely that estradiol affects the amount of norepinephrine released in the brain regions responsible for hormonal regulation. Signaling is critical to sexual behavior around ovulation. However, Karkanias' investigation now also points to possible causes for the more emotional and behavioral reactions to the hormones. Estradiol affects the amount of norepinephrine "seen" by the receptors by directly altering the number of these receptors.
The same receptors for norepinephrine found in rats are also found in human female brains. However, a direct connection between high and low estradiol levels and emotional behavior has not yet been established.
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