Influences of age on the positive inotropic effect mediated by alpha- and beta-adrenoceptors in rat ventricular strips.
The positive inotropic effect of phenylephrine (in the presence of atenolol) and isoprenaline was studied in isolated right ventricular strips obtained from Wistar rats aged 2 weeks, 3 months, and 26 months. The positive inotropic effects induced by phenylephrine and isoprenaline were higher in the 2-week-old than in the 3- or 26-month-old rats. The typical 'alpha-type' or 'beta-type' responses were induced by phenylephrine (plus atenolol) or isoprenaline, in all the age groups. The EC50 values for the alpha-mediated positive inotropic effect decreased with age, while the EC50 value for the positive inotropic effect of isoprenaline increased in the senescent heart. These results suggest an enhanced alpha-adrenergic sensitivity in the senescent heart.
Amerini
S
S
Fusi
F
F
Piazzesi
G
G
Mantelli
L
L
Ledda
F
F
Mugelli
A
A
D000375:Aging; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013268:Stimulation, Chemical
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D001262:Atenolol; D007545:Isoproterenol