VASOMOTOR REACTIVITY AND CATECHOLAMINE, ARGININE-VASOPRESSIN PLASMA-LEVELS DURING AGING AND DEVELOPMENT IN RATS

Vascular reactivity, heart rate responses to vasoconstrictor and/or va sodilatator agents and catecholamine and arginine vasopressin turnover were studied in normotensive Wistar Kyoto (WKY), spontaneously hypert ensive (SHR), normolipemic Brown Norway (BN) and spontaneously hyperli pemic Yoshida (YOS) anaesthetized rats at 2, 6 and 18 months of age. I n this study, we investigated whether ageing and development could aff ect cardiovascular reactivity to vasoactive substances and catecholami ne and arginine vasopressin turnover. No significant changes in the pr esser responses to noradrenaline and to carotid sinus baroreceptor sti mulation were observed nor were there significant alterations in refle x tachycardia and bradycardia. Arginine vasopressin plasma levels also did not change with ageing and development. On the other hand, the hy potensive responses to isoprenaline decreased in old rats, acetylcholi ne relaxation effect increased with ageing and development in some rat strains (BN and YOS) and catecholamine plasma levels increased with a geing and development. Our results indicate that during ageing and dev elopment, vascular responsiveness to vasoconstrictor and/or vasodilata tor agents, as well as amine turnover may increase, decrease or not ch ange at all depending on the neurotransmission system studied, and on the experimental model and/or animal tested.