Effects of Gonadal Hormones On Glutamatergic Circuits in the Retina

Abstract

Gonadal hormones function as neurosteroids in the retina; however, their targets in the retina have not yet been identified. The present study examined the effects of gonadal hormones on glutamatergic circuits in the retina. Extracellular glutamate concentrations, which correspond to the amount of glutamate released, were monitored using an enzyme-linked fluorescent assay system. Progesterone and pregnenolone both increased extracellular glutamate concentrations at a physiological concentration in pregnancy, whereas estrogen and testosterone did not. Synaptic level observations using a patch clamp technique revealed that progesterone increased the activity of glutamatergic synapses. We also investigated whether high concentrations of gonadal hormones induced changes in the retina during pregnancy. The present results indicate that progesterone activates glutamatergic circuits as a neurosteroid when its concentration is elevated in pregnancy.