Age-related changes in responses to nerve stimulation and catecholamines in isolated monkey cerebral arteries.

Mechanical responses to transmural electrical stimulation, nicotine, norepinephrine, and isoproterenol were compared in cerebral artery strips obtained from Japanese monkeys of different ages (1 mo, 1 yr, 4-7 yr, and greater than 7 yr old). Transmural electrical stimulation produced a contraction in the baby and juvenile monkey arteries contracted with prostaglandin F2 alpha, whereas the older monkey arteries responded to the stimulation with a relaxation. The stimulation-induced contraction was abolished or reversed to a relaxation by phentolamine; the relaxation was not influenced by propranolol and atropine but was abolished by tetrodotoxin, as was the response of the mature monkey arteries. Contractions caused by norepinephrine were greater in baby cerebral arteries than in the older monkey arteries; however, the apparent median effective concentration values did not differ. Middle cerebral artery contractions were greater than those of basilar arteries. The norepinephrine-induced contraction was suppressed by prazosin but not influenced by yohimbine. Isoproterenol (up to 10(-6) M) produced a greater relaxation in the baby arteries than in the older monkey arteries. It is suggested that adrenergic nerves innervating immature monkey cerebral arteries contribute to the regulation of vascular tone predominantly over nonadrenergic, noncholinergic vasodilator nerves, whereas the vasodilator nerves play a major role in the mature monkey arteries. alpha 1-Adrenoceptor subtype appears to be mainly involved in the norepinephrine-induced contraction of baby monkey cerebral arteries, as it is in that of the adult monkey arteries.