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

• Published in: Neuroendocrinology Vol. 68; no. 4; pp. 264 - 271
• Main Authors: Belmar, J, Cuellar, C, Llona, I, Arancibia, S, Kusch, C, Tapia-Arancibia, L, Pinter, A, Perez, H
• Format: Journal Article
• Language: English
• Published: 01.10.1998
• ISSN: 0028-3835
• DOI: 10.1159/000054374

Superfused frontal slices of cerebral cortex were preloaded with [ super(3)H]-norepinephrine ([ super(3)H]NE). Basal [ super(3)H]NE efflux and K super(+)-induced [ super(3)H]NE release were studied during the estrous cycle and in the presence of neurosteroids. Basal [ super(3)H]NE efflux showed estrous cycle-related variations, with lowest values found during estrus and diestrus II. Allopregnanolone (10 super(-9) M) potentiated basal [ super(3)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 [ super(3)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 [ super(3)H]NE efflux was no longer affected by the neurosteroid. In the presence of yohimbine (10 super(-6) M), the effect of allopregnanolone on basal efflux was potentiated only during the first 3 min but vanished thereafter. Allopregnanolone (10 super(-9) M) potentiated the K super(+)-induced [ super(3)H]NE release during estrus, but pregnenolone (10 super(-9) M) was ineffective, suggesting specificity of the neurosteroid. Yohimbine (10 super(-6) M) also potentiated K super(+)-induced [ super(3)H]NE release. When applied simultaneously with allopregnanolone (10 super(-9) M), a potentiating effect on [ super(3)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.