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      Allopregnanolone-Induced Modification of Presynaptic Basal and K +-Induced [ 3H]-Norepinephrine Efflux from Rat Cortical Slices during the Estrous Cycle

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          Superfused frontal slices of cerebral cortex were preloaded with [<sup>3</sup>H]-norepinephrine ([<sup>3</sup>H]NE). Basal [<sup>3</sup>H]NE efflux and K<sup>+</sup>-induced [<sup>3</sup>H]NE release were studied during the estrous cycle and in the presence of neurosteroids. Basal [<sup>3</sup>H]NE efflux showed estrous cycle-related variations, with lowest values found during estrus and diestrus II. Allopregnanolone (10<sup>–9</sup>  M) potentiated basal [<sup>3</sup>H]NE efflux from the 1st minute of its application; the effect of the steroid was still present after 20 min. This effect was also dependent upon the estrous cycle, since basal [<sup>3</sup>H]NE efflux was mainly increased during estrus diestrus I, and to a lesser degree only during proestrus. During diestrus II and after ovariectomy, basal [<sup>3</sup>H]NE efflux was no longer affected by the neurosteroid. In the presence of yohimbine (10<sup>–6</sup>  M), the effect of allopregnanolone on basal efflux was potentiated only during the first 3 min but vanished thereafter. Allopregnanolone (10<sup>–9</sup>  M) potentiated the K<sup>+</sup>-induced [<sup>3</sup>H]NE release during estrus, but pregnenolone (10<sup>–9</sup>  M) was ineffective, suggesting specificity of the neurosteroid. Yohimbine (10<sup>–6</sup>  M) also potentiated K<sup>+</sup>-induced [<sup>3</sup>H]NE release. When applied simultaneously with allopregnanolone (10<sup>–9</sup> M), a potentiating effect on [<sup>3</sup>H]NE release was observed. The present results suggest that allopregnanolone is a neurosteroid able to modulate norepinephrine release in the cerebral cortex in an estrous cycle-dependent manner, and that the effect could involve noradrenergic alpha-2 receptors.

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          Most cited references 7

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          Non-genomic and genomic effects of steroids on neural activity.

           Bruce McEwen (1991)
          Steroid hormones are recognized as producing their major long-term effects on cell structure and function via intracellular receptors acting on the expression of genes. There is now increasing evidence that steroids also affect the surface of cells and alter ion permeability, as well as release of neurohormones and neurotransmitters. Progesterone appears to be one of the most active of the steroids, and its naturally produced metabolites and some synthetic analogs show activities that are different from the parent steroid. Other steroids, such as estrogens and adrenal steroids and their naturally produced and synthetic analogs, also show membrane effects. Bruce McEwen reviews evidence that synergistic interactions occur between non-genomic and genomic actions of steroids.
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              In vitro progesterone effects on 3H-dopamine release from rat corpus striatum slices obtained under different endocrine conditions


                Author and article information

                S. Karger AG
                October 1998
                14 October 1998
                : 68
                : 4
                : 264-271
                a Laboratory of Biochemical Pharmacology, P. Catholic University of Chile and b Laboratory of Neural Systems, University of Santiago, Chile; c Laboratory of Brain Plasticity EP 628, CRNS, University of Montpellier II, France
                54374 Neuroendocrinology 1998;68:264–271
                © 1998 S. Karger AG, Basel

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                Page count
                Figures: 4, Tables: 1, References: 28, Pages: 8
                Reproductive Neuroendocrinology


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