Reactivity of isolated human cerebral arteries to biogenic amines

Serotonin (5-HT), histamine, norepinephrine, methoxamine and isoproterenol caused dose-dependent contraction of human cerebral arteries. The potency of 5-HT was greater among test agents in the basilar arteries, whereas it was equivalent to that of norepinephrine in human anterior, middle and posterior cerebral arteries. Acetylcholine and carbachol (10(-9)-10(-5) M) caused a negligible response in human cerebral arteries. Contractile response to 5-HT was greater in the distal rather than middle portion of the human basilar arteries while this order was reversed in the response to norepinephrine. Tyramine (10(-4) M) caused tonic contraction and nicotine (10(-4) M) and electrical transmural stimulation produced phasic contraction of arteries which were antagonized by adrenergic blocking agents. Adenine nucleotides failed to cause relaxation and only high concentration of adenosine caused a minute relaxation. However, papaverine and nitroglycerin caused marked relaxation. These results suggest that adrenergic mechanism may play a role in the regulation of vascular tone in human cerebral arteries.