TURNOVER RATE AND STIMULUS-EVOKED RELEASE OF DOPAMINE BY PROGESTERONEAND N-METHYL-D-ASPARTIC ACID IN RAT STRIATUM DURING PREGNANCY

The proposed modulatory role of progesterone on dopaminergic nerve ter minal activity in the striatum was examined in pregnant rats. Endogeno us dopamine concentration and the in vitro effect of exogenous progest erone in association with N-methyl-D-aspartic acid (NMDA) upon [H-3]do pamine release from striatal slices were determined. Striatal dopamine and 3,4-dihidroxyphenylacetic acid (Dopac) contents on day 5 of pregn ancy were significantly higher than those found at the other stages of pregnancy and proestrus. On days 5 and 15 of pregnancy, progesterone (400 nM) was able to enhance [H-3]dopamine release stimulated by NMDA (50 mu M) A similar effect was found in striatal slices from proestrus rats. In contrast, progesterone was without an effect on days 1, 10 a nd 20 of pregnancy and postpartum. The results suggest that an increas ed synthesis and/or release of dopamine takes place on certain days of pregnancy and, simultaneously, that there is a significant increase i n the responsiveness of striatal dopaminergic nerve terminals to excit atory inputs. They provide further support for a modulatory role of pr ogesterone in relation with a glutamatergic action on dopaminergic act ivity in the corpus striatum.