Abstract
1. The neurosteroids are compounds derived from steroid hormones and synthesized in the nervous system. They can modulate different neurotransmitter pathways. In previous work we demonstrated that progesterone modulates dopamine release induced by the glutamatergic agonist N-methyl-D-aspartic acid (NMDA). 2. The aim of this work was to evaluate a possible modulatory role of the progesterone metabolite allopregnanolone on NMDA-evoked [3H]dopamine release from corpus striatum slices obtained from cycling and ovariectomized female rats. 3. We used a dynamic superfusion method to evaluate the release of [3H]dopamine. Allopregnanolone at 50-600 nM was added to the superfusion buffer (Krebs-Ringer-bicarbonate-glucose. pH 7.4. with constant O2/CO2 gassing). The results are expressed as a percentage over basal [3H]dopamine loaded by the tissue. 4. Allopregnanolone (50 and 100 nM) increased the NMDA-evoked [3H]dopamine release from estrus rats. The remaining doses did not show significant changes in the pattern of release. This effect was not observed in diestrus rats. The ovariectomy abolished the facilitatory effect of allopregnanolone on NMDA-evoked 2 [3H]dopamine release. 5. Subcutaneous administration of exogenous estrogen (25 mg/rat) and progesterone (1 mg/rat) restored the facilitatory effect on dopaminergic input. 6. These results suggest that allopregnanolone is a neurosteroid able to modulate dopamine release in an ovarian-hormone-fluctuation-dependent manner and provide further support for a role of allopregnanolone as a modulator of glutamatergic-dopaminergic interaction in the corpus striatum.