Cocaine is one of the most abused illicit drugs worldwide.It is well known that the dopamine (DA) transporter is its major target;but cocaine also acts on other targets including nicotinic acetylcholine receptors (nAChRs).In this study,we investigated the effects of cocaine on a special subtype of neuronal nAChR,α3β4-nAChR expressed in native SH-SY5Y cells.α3β4-nAChR-mediated currents were recorded using whole-cell recordings.Drugs were applied using a computer-controlled U-tube drug perfusion system.We showed that bath application of nicotine induced inward currents in a concentration-dependent manner with an EC50 value of 20 μM.Pre-treatment with cocaine concentration-dependently inhibited nicotine-induced current with an IC50 of 1.5 μM.Kinetic analysis showed that cocaine accelerated α3β4-nAChR desensitization,which caused a reduction of the amplitude of nicotineinduced currents.Co-application of nicotine and cocaine (1.5 μM) depressed the maximum response on the nicotine concentrationresponse curve without changing the EC50 value,suggesting a non-competitive mechanism.The cocaine-induced inhibition of nicotine response exhibited both voltage-and use-dependence,suggesting an open-channel blocking mechanism.Furthermore,intracellular application of GDP-βS (via recording electrode) did not affect cocaine-induced inhibition,suggesting that cocaine did not alter receptor internalization.Moreover,intracellular application of cocaine (30 μM) failed to alter the nicotine response.Finally,cocaine (1.5 μM) was unable to inhibit the nicotine-induced inward current in heterologous expressed α6/α3β2β3-nAChRs and α4β2-nAChRs expressed in human SH-EP1 cells.Collectively,our results suggest that cocaine is a potent blocker for native α3β4-nAChRs expressed in SH-SY5Y cells.
展开▼
