The mechanism of midazolam-induced vasodilation of isolated rat aorta / 中华麻醉学杂志

ABSTRACT

Objective To investigate the direct effects of midazolam on vascular tension and the possible mechanism Methods Male Wistar rats weighing 200 250g were decapitated and the thoraco abdominal sect of aorta was removed and placed in modified Kreb's solution balanced with 95% O 2 and 5% CO 2 After removal of surrounding connective tissue and fat, the aorta was cut into rings 3 4mm in length The endothelium of some of the aorta rings were denuded Aorta rings were suspended in a 37℃ bath of Kreb's solution which was continuously balanced with 95% O 2 and 5% CO 2 One end of the ring was fixed and the other end was connected to a tension monitor through a tension transducer The intactness of endothelium was tested and confirmed by addition of phenylephrine(PE) first and then acetylcholine Aorta rings of each animal were divided into four groups: endothelium intact control group(Ⅰ); endothelium intact experiment group(Ⅱ);endothelium denuded control group(Ⅲ);and endothelium denuded experiment group(Ⅳ) The experiment was carried out in two parts: Part Ⅰ: the effect of midazolam (3?10 -6 ,10?10 -6 ,30?10 -6 ,100?10 -6 mol/L) on endothelium intact and denuded aorta rings which were precontracted with PE(10 -6 mol/L); part Ⅱ: before different concentrations of midazolam was added, the endothelium intact rings were pretreated with methylene blue(10 -5 mol/L) and the endothelium denuded rings were pretreated with verapamil(5?10 -6 mol/L) or teraethylammonium(TEA,5?10 -3 mol/L).Results The four concentrations of midazolam examined produced relaxation in both endothelium intact and denuded rings Relaxation of endothelium denuded rings was less than that of endothelium intact rings (P0 05) When pretreated with TEA, midazolam produced greater relaxation in endothelium denuded rings(P