IN-VITRO PROGESTERONE EFFECTS ON H-3 DOPAMINE RELEASE FROM RAT CORPUSSTRIATUM SLICES OBTAINED UNDER DIFFERENT ENDOCRINE CONDITIONS

The release of dopamine (DA) from corpus striatum is affected by the e ndocrine state of the animal being progesterone suggested as a potenti al 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 highl y complexes. Considering that DA recently incorporated and/or syntheti zed is preferentialy used we have characterized the effect of progeste rone in vitro on the K+-induced release of H-3-dopamine)H-3-DA) from r at corpus striatum slices. These were obtained during the estrous cycl e or under conditions of high or low levels of endogenous progesterone (pregnant and ovariectomized rats). The release of H-3-DA was indepen dent of the cycle. However, progesterone in vitro modified the induced release in a cyle-dependent way. Low concentrations of the hormone (1 00-200 mM) reduced the K+ (30 mM) effect while higher doses (300-500 m M) were facilitatories. After 7 days of ovariectomy, the induced relea se of H-3-DA was unchanged while in pregnant rats it was found decreas ed. In both cases the inhibitory effect of the hormone dissapeared. Bo th progesterone (200 nM) and omission of Ca++ from the superfusion med ium did not modified tyramine(20 muM) or K+ induced release, respectiv ely. Data suggest that the pool of DA, related to exocytotic mechanism of release, could be specifically affected by progesterone, in a bimo dal way, probably through independent genomic and non-genomic influenc es.