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1 Laboratoire de Pharmacologie
Cardio-vasculaire,
In male Wistar rats, the in vitro
vasoconstrictor response of the perfused tail artery elicited by
norepinephrine or serotonin decreased with age (24 mo old vs. 3 mo
old), whereas the fluorescent signal (fura 2) produced by intracellular
calcium (Ca2+i) mobilization
increased. Both vasoconstriction and the increase in intracellular
calcium concentration elicited by a
high-K+, depolarizing solution
were unaffected by aging. Pertussis toxin, a G protein inhibitor, had
no effect on vasoconstriction induced by high
K+ but diminished vasoconstrictor
responses to norepinephrine in 3- and 12-mo-old animals but not in
24-mo-old animals. Pertussis toxin had no effect on
Ca2+i mobilization. The sensitivity of
receptor activation to pertussis toxin in tail arteries from 24-mo-old
animals was restored by pretreatment with the
-adrenoceptor
antagonist nicergoline. Nicergoline had no effect on vasoconstriction
induced by high K+. Plasma
norepinephrine concentration rose with age; nicergoline had no effect
on this rise. We suggest that aging leads to a decrease in the
intracellular G protein-modulated amplification of vasoconstriction produced by receptor activation and that this could be linked to the
hyperadrenergic state. Ca2+
sensitivity can be restored by chronic treatment with an
-adrenoceptor antagonist.
age; nicergoline; serotonin; norepinephrine
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