Vasomotor reactivity and catecholamine, arginine vasopressin plasma levels during ageing and development in rats

Vascular reactivity, heart rate responses to vasoconstrictor and/or vasodilatator agents and catecholamine and arginine vasopressin turnover were studied in normotensive Wistar Kyoto (WKY), spontaneously hypertensive (SHR), normolipemic Brown Norway (BN) and spontaneously hyperlipemic Yoshida (YOS) anaesthetized rats at 2, 6 and 18 months of age. In this study, we investigated whether ageing and development could affect cardiovascular reactivity to vasoactive substances and catecholamine and arginine vasopressin turnover. No significant changes in the pressor responses to noradrenaline and to carotid sinus baroreceptor stimulation were observed nor were there significant alterations in reflex tachycardia and bradycardia. Arginine vasopressin plasma levels also did not change with ageing and development. On the other hand, the hypotensive responses to isoprenaline decreased in old rats, acetylcholine relaxation effect increased with ageing and development in some rat strains (BN and YOS) and catecholamine plasma levels increased with ageing and development. Our results indicate that during ageing and development, vascular responsiveness to vasoconstrictor and/or vasodilatator agents, as well as amine turnover, may increase, decrease or not change at all depending on the neurotransmission system studied, and on the experimental model and/or animal tested.