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Noradrenaline contracts arteries by activating voltage-dependent calcium channels.
Nelson MT, Standen N, Brayden J, Worley J
Nature. 1988;336( 6197):382-5.
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Abstract
Noradrenaline (NA) regulates arterial smooth muscle tone and hence blood vessel diameter and blood flow. NA apparently increases tone by causing a calcium influx through the cell membrane. Two calcium influx pathways have been proposed: voltage-activated calcium channels and NA-activated calcium-permeable channels that are voltage-insensitive. Although voltage-activated calcium channels have been identified in arterial smooth muscle, voltage-insensitive calcium channels activated by NA have not. We show here that NA contractions of rabbit mesenteric arteries increase with depolarization. The increase parallels the elevation of open-state probability (P0) of single, voltage-dependent calcium channels. The action of noradrenaline can be explained by NA-activating voltage-dependent calcium channels, rather than by opening a second type of channel. We show directly that NA increases the open-state probability of single calcium channels. Thus, in the presence of NA, calcium entry through voltage-dependent calcium channels can regulate smooth muscle tone at physiological membrane potentials. These results may have relevance to pathophysiological conditions such as hypertension.
Keyword(s)
Animals; Membrane Potentials; Rabbits; pharmacology: Norepinephrine; physiology: Calcium Channels; physiology: Mesenteric Arteries; physiology: Muscle, Smooth, Vascular