Blockade of ionotropic receptor responses by progesterone in the ganglion cells of Aplysia.

To compare nongenomic effects of progesterone on various receptor responses of neurons, Aplysia ganglion cells were pretreated with 30 microM progesterone for 5 min and various receptor responses were tested using a conventional voltage-clamp method. Progesterone reduced nicotinic receptor-activated Na(+)-currents, nicotinic receptor-activated Cl(-)-currents, gamma-aminobutyric acid receptor-activated Cl(-)-currents, and dopamine receptor-activated Na(+)-currents. These depressant effects are similar at two different agonist concentrations.