Rapid Nongenomic Effect of Corticosterone on Neuronal Nicotinic Acetylcholine Receptor in PC12 Cells

The effects of corticosterone, a natural glucocorticoid of rat, on the acetylcholine (ACh)-induced current (IACh) were studied in pheochromocytoma (PC12) cells by using whole-cell clamp technique. The IACh proved to be generated through neuronal nicotinic receptor. ACh (30 μM) induced an inward current at a holding potential of −80 mV. When cells were preincubated with corticosterone (0.1–100 μM) for 4 min, an inhibitory effect of corticosterone on the peak of IACh was found. This effect was reversible, concentration-dependent, and voltage-independent. Intracellular application of corticosterone through the patch electrode did not affect the IACh. Extracellular application of 10 μM corticosterone neither shifted the dose–response curve of the peak IACh to the right (dissociation constant (Kd) = 16.5 μM) nor affected its coefficient (1.8) but inhibited the curve amplitudes by ∼49% in the cells pretreated with corticosterone for 4 min. Bovine serum albumin-conjugated corticosterone (0.1–10 μM) had the inhibition similar to corticosterone. The inhibitor of transcription, actinomycin D (10 μM), and the protein synthesis inhibitor, cycloheximide (50 μM), had no effect on the inhibition induced by corticosterone on IACh. These results suggest that corticosterone has rapid inhibitory effect on IACh in PC12 cells, which is mediated by a nongenomic mechanism. It indicates that corticosterone binds to the specific site on the outer cell membrane, probably on the neuronal nicotinic receptor-coupled channel, and inhibits the IACh in a noncompetitive manner, thus controlling the immediate catecholamine release from the sympathetic cells.