[The properties and sensitivity to acetylcholine of PC12 cells differentiated with NGF].

AIM AND METHODS: The properties and sensitivity to acetylcholine of PC12 cells differentiated with nerve growth factor (NGF) have been investigated by using whole-cell clamp technique. RESULTS: When cultured in the presence of NGF, PC12 cells not only differentiated to resemble sympathetic neurons morphologically, but also developed electrical excitability. NGF-treated PC12 cells were highly sensitive to ACh than untreated cells. The I(Ach) proved to be generated by nAChR by pharmacological identification. Nicotinic receptor was characterized by desensitization. The macroscopic I(ACh) was inward rectified and concentration dependent. CONCLUSION: PC12 cells are easily cultured and provides a homogenous population of cells. When culture in NGF, they differentiate to sympathetic-like neurons that contain on their surface neuronal nAChR, it can be used as good model system for studying regulation of a sympathetic neuronal nAChR.

Decrease in acetylcholine-induced current by neomycin in PC12 cells.

The effects of neomycin, one of the aminoglycoside antibiotics, on the acetylcholine (ACh)-induced current (I(ACh)) were studied in pheochromocytoma cells by using the whole-cell clamp technique. The I(ACh) proved to be generated through neuronal nicotinic receptor. ACh (30 microM) induced an inward current at a holding potential of -80 mV. When cells were treated with neomycin (0.01-1 mM) and ACh (30 microM) simultaneously, an inhibitory effect of neomycin on the peak of I(ACh) was found. This effect was fast, reversible, and concentration dependent. Pretreatment with neomycin for 3-8 min had no effect on the inhibition of I(ACh) induced by neomycin. External application of 0.1 mM neomycin neither shifted the dose-response curve of the peak I(ACh) to the right (dissociation constant (K(d)) = 16.5 microM) nor affected its coefficient (1.8) but inhibited the curve amplitudes by approximately 33%. Stimulated protein kinase C activation by using an exogenous activator produced inhibition of I(ACh), while using protein kinase C inhibitor (PKCI 19-31) had no effect on the inhibition of I(ACh) induced by neomycin. These results suggest that neomycin has an inhibitory effect on I(ACh) without the involvement of phospholipase C. It indicates that neomycin binds to a specific site on the cell membrane, probably on the neuronal nicotinic receptor-coupled channel, and inhibits the I(ACh) in a noncompetitive manner, thus controlling the immediate catecholamine release from the sympathetic cells.

Modulation of neuronal nicotinic acetylcholine receptors by glucocorticoids.

AIM: To investigate the nongenomic effect of the glucocorticoid corticosterone on nicotinic acetylcholine receptor (nAChR) in PC12 cells. METHODS: The acetylcholine (ACh)-induced current was measured on nerve growth factor differentiated PC12 cells using whole-cell patch-clamp techniques. RESULTS: The ACh-induced current (IACh) proved to be generated through neuronal nAChR. When ACh (30 micromol/L) was applied simultaneously with corticosterone (0.1 - 10 micromol/L), the decay of IACh was faster with slight inhibition on the peak current amplitude. Pretreating PC12 cells with corticosterone augmented the inhibition on the peak IACh and did not alter receptor desensitization. Bovine serum albumin-conjugated corticosterone (0.1 - 10 micromol/L) had the inhibition similar to corticosterone. The rapid effect induced by corticosterone was reversible, concentration-dependent, and voltage-independent. CONCLUSION: Corticosterone has rapid inhibitory effect on IACh, 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.