Comparison of the Effect of α₁- and α₂-Adrenoceptor Agonists and Antagonists on Muscle Contractility of the Rabbit Abdominal Aorta in vitro

Abstract

The aim of the study was to demonstrate the effect of selected agonists and antagonists of alpha-adrenergic receptors on muscle contractility of the rabbit abdominal aorta in vitro with particular emphasis on alpha2-adrenergic receptor subtypes. The study was conducted on 30 New Zealand breed rabbits from which specimens of the abdominal aorta were collected. The sections were set up in an automatic water bath in a Krebs-Henseleit buffer at 37 degrees C. The experiments showed that alpha1-adrenergic receptors played the main role in the contractile response ofthe rabbit abdominal aorta. Stimulation of alpha1-adrenergic receptor by administration ofphenylephrine resulted in an increase in smooth muscle tonus ofthe rabbit abdominal aorta by an average of 4.75 mN. The reaction after stimulation of alpha2-adrenergic receptors by similar doses of their agonists was much weaker. Prolonged tissue response time and time needed to reach maximum tonus for alpha2-adrenergic receptor agonists were observed. The obtained results confirm the thesis that the alpha1-adrenergic receptor is the most important factor controlling the contractility of the rabbit abdominal aorta, but the alpha2-adrenergic receptor is also involved in maintaining muscle tissue tonus.

VASCULAR MECHANISMS OF TRITERPENOID SAPONINS ISOLATED FROM Passiflora quadrangularis L.

“…This leaves to suppose that site of action of those metabolites places at vasculature media layer. Given that alpha adrenergic receptors are located in smooth muscle (α 1 , α 2 ) (21,22), and they are connected to calcium signalling (23). compounds 1 and 2 could mediate calcium currents activation on smooth muscle via α stimulation, being key metabolites responsible for the global effect seen with P. quadrangularis L.…”