The mechanisms of propofol-mediated hyperpolarization of in situ rat mesenteric vascular smooth muscle.
Previously, we reported that propofol hyperpolarizes vascular smooth muscle (VSM) cells of small arteries and veins. The current study was designed to determine whether propofol-mediated hyperpolarization is the result of specific effects on potassium channels known to exist in VSM and on steps in the intracellular nitric oxide (NO), cyclic guanosine monophosphate (cGMP), and cyclic adenosine monophosphate (cAMP) second messenger pathways. VSM transmembrane potentials (E(m)) were measured in situ in sympathetically denervated, small mesenteric arteries and veins of Sprague-Dawley rats. Effects of propofol on VSM E(m) were determined before and during superfusion with specific inhibitors of VSM calcium-activated (K(Ca)), adenosine triphosphate-sensitive (K(ATP)), voltage-dependent (K(v)), and inward rectifying (K(IR)) potassium channels and with endogenous mediators of vasodilation. Propofol significantly hyperpolarized VSM in small mesenteric vessels. This hyperpolarization was abolished on inhibition of K(Ca) and K(ATP) channel activity and on inhibition of NO and cGMP (but not cAMP). Assuming a close inverse correlation between the magnitude of VSM E(m) and contractile force, these results suggest that propofol induces hyperpolarization and relaxation in denervated, small mesenteric vessels by activation of K(Ca) and K(ATP) channels. Such channel activation may be mediated by activation of NO and cGMP, but not cAMP, second messenger pathways.


CONCLUSIONS
The results of this study indicate that propofol-mediated hyperpolarization in vascular smooth muscle can be attributed to the activation of calcium-activated, adenosine triphosphate-sensitive potassium channels, the nitric oxide, and cyclic guanosine monophosphate pathways.
Nagakawa
Tamotsu
T
*Department of Anesthesiology, Toyama Medical and Pharmaceutical University, Toyama, Japan, and the †Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin.
Yamazaki
Mitsuaki
M
Hatakeyama
Noboru
N
Stekiel
Thomas A
TA
D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000502:physiology; D006152:Cyclic GMP / Q000037:antagonists & inhibitors / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000187:drug effects*; D008642:Mesenteric Veins / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052250:Nitric Oxide Synthase Type III; D015221:Potassium Channels / Q000187:drug effects; D015742:Propofol / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015290:Second Messenger Systems / Q000187:drug effects; D013562:Sympathectomy; D013564:Sympathetic Nervous System / Q000502:physiology
D018686:Anesthetics, Intravenous; D004791:Enzyme Inhibitors; D015221:Potassium Channels; D009569:Nitric Oxide; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester; D015742:Propofol