[Rapid inhibitory effect of glucocorticoids on ACh-induced current in rat phaeochromocytoma cells].

A rapid effect of glucocorticoids (GC) on acetycholine-induced current in rat phaeochromocytoma (PC12) cells and its possible mechanism were investigated by whole-cell clamp technique. The results are as follows: The acetylcholine-induced current (IACh) of PC12 cells was proved to be generated through nicotinic ACh receptor by pharmacological identification. ACh (30 mumol/L) induced an inward current at a holding potential (Vh) of -80 mV. The inhibitory effect of corticosterone (B) on IACh was weak when 10(-5) mol/L B and ACh were simultaneously applied extracellularly. Pretreatment of PC12 cells with B could augment the inhibitory effect on peak IACh, and this dose-dependent effect was reversible. At the same concentration of GC, the rank of the inhibitory potency was B > dexamethasone (Dex) > hydrocortisone (F). Extracellular application of B-BSA could also inhibit IACh rapidly. Taken together, it is suggested that GC induced rapid inhibitory effects on IACh in PC12 cells are probably mediated by a nongenomic mechanism. The inhibitory effect of various GC on IACh are different.