AGE-RELATED-CHANGES IN RESPONSE OF RABBIT ISOLATED AORTAE TO VASOACTIVE AGENTS

In helically‐cut strips of aortae from rabbits of different ages (2 to 360 days old), responses to vasoconstrictor and vasodilator agents were compared. The passive tension developed by the same magnitude of stretch was markedly less in aortae from immature rabbits than in aortae from mature rabbits. Contractile responses to noradrenaline and K+ increased with age in the range from 2 to 90 days. High concentrations of noradrenaline (10−5 and 5 × 10−5m) produced relaxation of aortic strips from immature rabbits (2 to 30 days). The response to histamine was not altered with age. Age‐dependent reductions (90 to 360 days) in the response to 5‐hydroxytryptamine were observed. Relaxations induced by isoprenaline of aortic strips contracted with prostaglandin F2at increased with age in the range from 2 to 30 days but decreased with age from 30 to 360 days. Similar age‐related alterations in the relaxant response to adenosine were observed. It is concluded that aortae from immature rabbits are more distensible than those from mature rabbits; α‐adrenoceptors mature during an early postnatal period (2 to 30 days), and 5‐hydroxytryptamine receptor mechanisms deteriorate with age (older than 90 days). The β‐receptor mechanism does not seem to alter greatly with age. 1978 British Pharmacological Society