Cellular and molecular effects of steroid hormones on CNS excitability.

The steroid hormones 17beta-estradiol (estradiol) and progesterone not only regulate the reproductive system but have other central nervous system effects that can directly affect a variety of behaviors. Generally, estradiol has been shown to have activating effects, including the ability to increase seizure activity, while progesterone has been shown to have depressant effects, including anticonvulsant properties. Because levels of these hormones fluctuate across the menstrual cycle, it is important to understand how changes in these hormone levels may influence levels of excitability in the brain, especially in women who have seizure patterns that are related to their menstrual cycle, a phenomenon known as catamenial epilepsy. This paper reviews the effects of estradiol and progesterone on excitatory and inhibitory neurotransmitters, respectively, and the possible cellular and molecular mechanisms underlying the changes in brain excitability mediated by these hormones.