Vascular smooth muscle contraction initiated by postsynaptic alpha 2-adrenoceptor activation is induced by an influx of extracellular calcium.
Vasoconstriction in pithed, normotensive rats elicited via stimulation of postsynaptic alpha 2-adrenoceptors by B-HT 920 was antagonized by EDTA and the calcium antagonists nifedipine, D 600 and verapamil, whereas pressor responses to the alpha 1-agonist methoxamine were unaffected. This indicates that vasoconstriction in vivo initiated via postsynaptic alpha 2-adrenoceptors requires an influx of extracellular calcium. Thus, the antihypertensive effect of calcium antagonists may be based upon a diminution of vascular tone maintained by postsynaptic alpha 2-adrenoceptors.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects
D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D002118:Calcium