Progesterone effects upon dopamine release from the corpus striatum of female rats. I. Evidence for interneuronal control.

In the present experiment, we examined whether progesterone modifies dopamine (DA) release from superfused corpus striatal (CS) tissue fragments of ovariectomized estrogen-primed rats as result of a direct interaction with dopaminergic nerve terminals or through interneurons within the CS. In Expt. I, an in vitro pulsatile infusion of progesterone (2 ng/ml) directly into superfusion chambers containing CS fragments resulted in a statistically significant increase in DA release (P less than 0.008). No such stimulation was obtained following a continuous progesterone infusion or during control superfusions receiving no progesterone. In an effort to examine a direct action of progesterone on DA terminals in Expt. II, tetrodotoxin (TTX, 1 microM) was added to the Superfusion medium to block the activity of interneurons within the CS. TTX completely abolished the effect of pulsatile progesterone on DA release. These results indicate that the stimulatory action of progesterone on in vitro DA release from CS fragments is apparently exerted through activation of interneurons which discriminately respond to a specific (pulsatile) mode of progesterone infusion.