AGE-DEPENDENT ALTERATION IN THE RESPONSE OF ISOLATED RABBIT BASILAR ARTERIES TO VASOACTIVE AGENTS

Abstract

Responses to vasoactive agents were compared in helical strips of basilar arteries isolated from rabbits, 15-360 days of age, which were stretched under optimal resting forces. Contractions induced by serotonin, histamine, norepinephrine, angiotensin II and K+ increased with increasing age. The maximum forces developed by these drugs relative to those by 50 mM K+ and ED50 values of these drugs were not significantly different in the arteries from mature and immature rabbits; only the response to serotonin at day 360 was significantly less. Basilar arteries contracted with histamine relaxed in response to isoproterenol; the relaxing effect was suppressed by treatment with 10-6 M propranolol and was inversely related to age. Relaxations induced by adenosine and prostaglandin E1 did not significantly differ in the arteries from rabbits of different ages. Relaxations induced by small amounts of K+ (0.5-10 mM) increased with age; the relaxations were suppressed by ouabain. The cerebroarterial relaxation related specifically to the .beta.-adrenergic mechanism is reduced with increasing age. The electrogenic Na+ pump mechanism appears to mature in rabbit basilar arteries during an early postnatal period.