Calmodulin antagonist W7 directly inhibits f-type current in rabbit sino-atrial cells.
As reported for cyclic nucleotide-gated channels in sensory neurons, we investigated the action of Ca2+-calmodulin and calmodulin antagonist (W7) on the apparent affinity of pacemaker (I(f)) channels for cAMP. In this study, we used the patch-clamp technique in inside-out macro-patch configuration in rabbit sino-atrial cells. Intracellular calmodulin perfusion had no effect on f-channel activity and did not change the cAMP-induced I(f) activation shift. Nevertheless, W7 decreased maximal conductance and induced a voltage shift of the current activation curve towards negative potentials. W7 did not modify the positive shift caused by cAMP, and cAMP did not prevent the effects of W7. Contrary to the cyclic nucleotide-gated channel, the f-channel is not directly modulated by Ca2+-calmodulin. The data suggest that W7 alters the voltage-dependent properties of I(f)independent of cAMP binding. This agent opens the pathway for a new family of bradycardic drugs.
Chatelier
Aurélien
A
Institut de Physiologie et Biologie Cellulaires, CNRS UMR 6187, Université de Poitiers, 86022 Poitiers Cedex, France.
Renaudon
Barbara
B
Bescond
Jocelyn
J
El Chemaly
Antoun
A
Demion
Marie
M
Bois
Patrick
P
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D002147:Calmodulin / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008564:Membrane Potentials / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011817:Rabbits; D012849:Sinoatrial Node / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology*
D002147:Calmodulin; D013449:Sulfonamides; C017967:W 7; D000242:Cyclic AMP; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium