Hyperpolarization caused by serotonin contributes to endothelium-dependent relaxations in the porcine coronary artery.
OBJECTIVE
The present study was designed to investigate the contribution of membrane hyperpolarization to endothelium-dependent relaxations induced by serotonin in the porcine coronary artery.


METHODS
Rings with and without endothelium of porcine coronary arteries were suspended in conventional organ chambers for the measurement of isometric force. The cell membrane potential of the vascular smooth muscle cells was measured using glass microelectrodes, in the presence of indometacin, ketanserin, and/or N omega-nitro-L-arginine.


RESULTS
Serotonin induced a transient endothelium-, and concentration-dependent relaxation in rings contracted with prostaglandin F2 alpha in the presence of N omega-nitro-L-arginine (maximal relaxation: 19%). The N omega-nitro-L-arginine resistant relaxation was abolished by high K+ and tetrabutylammonium chloride. Serotonin also caused an endothelium-, concentration-dependent membrane hyperpolarizations with a maximal amplitude of -8.8 mV. The nitro-L-arginine resistant relaxations and hyperpolarizations were abolished by methiothepin, but not by glibenclamide. The time course of the endothelium-dependent relaxations and hyperpolarizations was similar.


CONCLUSIONS
These results suggest a contribution of cell membrane hyperpolarization to the endothelium-dependent relaxations induced by serotonin in the porcine coronary artery.
Park
S J
SJ
Center for Experimental Therapeutics, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Nakashima
M
M
Nagao
T
T
Vanhoutte
P M
PM
D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects; D004730:Endothelium, Vascular / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008719:Methiothepin / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D026902:Potassium Channel Blockers; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013552:Swine
D026902:Potassium Channel Blockers; D000644:Quaternary Ammonium Compounds; D012702:Serotonin Antagonists; D012701:Serotonin; D008719:Methiothepin; C009405:tetrabutylammonium