In vitro progesterone effects on 3H-norepinephrine release from rat cerebral cortex slices.

The effect of progesterone in vitro (0.05-5 microM) on K(+)-induced, Ca(2+)-dependent release of 3H-NE from brain slices obtained from the occipital region of rats, during the oestrous cycle or 7 days after ovariectomy or on the fifth day of pregnancy was studied. The hormone reduced the K+ (20 mM) effect in all the stages of the cycle, but did not modify the reduced release found after ovariectomy or pregnancy or the release induced from male slices. Yohimbine blocked the effect of progesterone. The results suggest the releasing process of norepinephrine in the cerebral cortex as a target for progesterone modulatory influences on brain function.