Propofol Relaxes Isolated Rat Aorta through BKCa Activation.

Propofol is an intravenous anesthetic that can be used for the induction and maintenance of anesthesia. In the present study, it was aimed to investigate the mechanism of vasodilator action of propofol in the rat aorta (RA).

The RA rings were suspended in isolated organ baths and tension was recorded isometrically. First, potassium chloride (KCl) and phenylephrine (PE) were added to organ baths to form precontraction. When the precontractions were stable, propofol (1, 10, and 100 μM) was added cumulatively to the baths. The antagonistic effect of propofol on KCl (45 mM), PE (1 μM), 5-hydroxytryptamine (5-HT) (30 μM), and calcium chloride (CaCl₂) (10 μM to 10 mM) induced contractions in the vascular rings were investigated. Propofol-induced relaxations were also tested in the presence of the K⁺ channel inhibitors tetraethylammonium (TEA, 1 mM), glibenclamide (GLI, 10 μM), 4-aminopyridine (4-AP, 1 mM), and barium chloride (BaCl₂, 30 μM).

Preincubation with propofol (1, 10, and 100 μM) did not affect the basal tone but inhibited the contraction induced by KCl, PE, 5-HT, and CaCl₂-induced contractions. Propofol-induced relaxation was not effected by 4-AP, GLI, and BaCl₂. However, TEA inhibited propofol-induced relaxations significantly.

The propofol induces relaxation in contracted RA and inhibits KCl, PE, 5-HT, and CaCl₂-induced contractions. The results demonstrate that the mechanism of action of propofol-induced vasodilation in the RA may be related to large conductance Ca²⁺-activated K⁺ channel activation.