In vitro progesterone effects on 3H-dopamine release from rat corpus striatum slices obtained under different...

The release of dopamine (DA) from corpus striatum is affected by the endocrine state of the animal being progesterone suggested as a potential hormonal modulatory signal. Most of its actions have been described on endogenous DA release induced by amphetamine. However, the release of DA and the mechanism of the drug effect have been shown to be highly complexes. Considering that DA recently incorporated and/or synthetized is preferentially used we have characterized the effect of progesterone in vitro on the K(+)-induced release of 3H-dopamine (3H-DA) from rat corpus striatum slices. These were obtained during the estrous cycle or under conditions of high or low levels of endogenous progesterone (pregnant and ovariectomized rats). The release of 3H-DA was independent of the cycle. However, progesterone in vitro modified the induced release in a cycle-dependent way. Low concentrations of the hormone (100-200 mM) reduced the K+ (30 mM) effect while higher doses (300-500 mM) were facilitatories. After 7 days of ovariectomy, the induced release of 3H-DA was unchanged while in pregnant rats it was found decreased. In both cases the inhibitory effect of the hormone disappeared. Both progesterone (200 nM) and omission of Ca++ from the superfusion medium did not modified tyramine (20 microM) or K+ induced release, respectively. Data suggest that the pool of DA, related to exocytotic mechanism of release, could be specifically affected by progesterone, in a bimodal way, probably through independent genomic and non-genomic influences.