Share on vk Share on google_plusone_share Share on twitter Share on email More Sharing Services Stimulation of α1-adrenoreceptors inhibits myocardial contractility in rats

Abstract

The exact role of α1-adrenoreceptors (α1-AR) as myocardial contractility modulators is still not clear. We studied the effects of α1-AR stimulation with methoxamine hydrochloride (Sigma) on the myocardial contractility ex vivo and in vitro: on the isolated heart (Langendorff's model) and on the atrium and ventricular myocardium strips in rats, respectively. The experiments were performed on random-bred albino 20-week-old rats (n = 28) with the average weight of 200–250 g. The contractility force (F) of myocardium strips was measured in grams (g). The contractility of isolated heart was measured as pressure in the left ventricle (mm Hg). All the studied concentrations of methoxamine (10–9–10–6 М) inhibited the contractility of the myocardium strips of rats' atria and ventricles. The stimulation of α1-AR with methoxamine (10–9 and 10–8 М) led to a decrease in the left ventricular pressure of the isolated heart in rats. The intensity of the negative inotropic effects was proportionate to the agonist concentration.

Keywords

• α1-adrenoreceptors
• heart
• myocardial contractility
• rats