[Adrenergic and cholinergic mechanisms of the contractile reactions of major blood vessels].

Epinephrine, norepinephrine, and isoproterenol induced circular contraction of isolated segments of canine intracerebral internal carotid artery. The alpha--and beta-antagonists inhibited the effects of catecholamines. Acetylcholine showed dual effects involving both dilation (5.10(-12)--5.10(-9) g/ml) and contraction 5.10(-8) g/ml and higher). Atropine inhibited both effects. The K+ depolarization abolished the contractile effects of norepinephrine and acetylcholine. The blockade of calcium permeability by Mn++ abolished the contractile effects of sympathetic and parasympathetic mediators.