Estrogen evokes a rapid effect on intracellular calcium in neurons characterized by calcium oscillations in the arcuate nucleus

Rapid estrogen effects became an interesting topic to explain estrogen effects not associated with the classical nuclear pathway. The rapid estrogen effect on intracellular calcium oscillations was characterized in neurons of the arcuate nucleus. Ratiometric calcium imaging (fura-2AM) was used to measure intracellular calcium in brain slices of female Swiss Webster mice (median of age 27 days p.n.). Calcium oscillations were dependent on intracellular calcium and also on calcium influx from the extracellular space. The perfusion of slices with calcium-free solution inhibited spontaneous calcium oscillations. The metabotropic glutamate receptor agonist t-ACPD (5 mu M) and low concentrated ryanodine (100 nM) induced intracellular calcium release when slices were perfused with calcium-free solution. 17 beta-estradiol (10 nM) also induced intracellular calcium release in calcium-free ACSF. This effect was inhibited by the preceding administration of thapsigargin (2 mu M) indicating the association of the rapid estrogen effect with intracellular calcium stores. The administration of the non-selective phospholipase C-inhibitor ET-18 (30 mu M), but not U73122 (10 mu M), and the inhibition of protein kinase A by H-89 (0.25 mu M) suppressed the rapid estrogen effect. Analyses indicated a qualitative, but not quantitatively significant effect of 17 beta-estradiol on calcium oscillations.