Ca-dependent action of cocaine on K current in freshly dissociated dorsal root ganglia from rats.
The actions of cocaine on K currents were analyzed in enzymatically dissociated neurons from adult rat dorsal root ganglia. The whole cell voltage clamp configuration was used to determine that in the presence of Ca cocaine inhibited a K conductance that was activated from a holding potential of -55 mV. The cocaine concentration that decreased K currents half-maximally was 18 microM. At a concentration of 40 microM, cocaine had no significant effect on K current remaining in the absence of external Ca, whereas at 80 microM a significant 17% depression of this current was observed. Large transient K currents occurring with depolarizations from -90 mV were also resistant to 40 microM cocaine, suggesting that cocaine specifically inhibits a Ca-dependent K current. Ca currents elicited from a holding potential of -55 mV were largely unaltered by 40 microM cocaine. The data suggest that cocaine may be a useful tool for experimental blockage of Ca-dependent K currents and also provide additional insight into the overall actions and toxicity of the drug.
Grossie
J
J
Department of Physiology, Ohio State University College of Medicine, Columbus 43210-1218.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D003042:Cocaine / Q000494:pharmacology*; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009994:Osmolar Concentration; D011188:Potassium / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D003042:Cocaine; D011188:Potassium; D002118:Calcium