The action of caffeine on inward barium current through voltage-dependent calcium channels in single rabbit ear artery cells

✍ Scribed by A. D. Hughes; S. Hering; T. B. Bolton

• Publisher: Springer
• Year: 1990
• Tongue: English
• Weight: 570 KB
• Volume: 416
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00370755

✦ Synopsis

The effect of caffeine on inward current carried by barium ions through voltage-dependent calcium channels has been investigated in single rabbit ear artery cells using whole-cell voltage-clamp techniques. Caffeine (1 -30 mM) caused a rapid and reversible concentration-dependent blockade of barium current and a related compound, 3-isobutyl-l-methylxanthine (IBMX), was a more potent inhibitor of barium current. Caffeine-induced inhibition of barium current showed no voltage-or usedependence and caffeine did not alter the steady-state inactivation of barium current. The effect of caffeine was not blocked by extracellular or by intracellular ryanodine or inclusion of both 5 mM 1,2-bis(2-aminophenoxy)ethane N,N,N',N',-tetraacetic acid (BAPTA) and 2 mM ethylene glycol-bis(/3-amino ethyl ether) N,N,N',Nf,tetraacetic acid (EGTA) in the intracellular solution. Rolipram and M&B 22984, non-xanthine inhibitors of phosphodiesterase, did not diminish inward barium current. The data indicate that caffeine and IBMX block voltage-operated calcium channels and it is suggested that this is due to a direct interaction of methylxanthines with the calcium channel.