EFFECTS OF PREANESTHETIC AND ANESTHETIC DRUGS ON ENDOTHELIUM-DEPENDENT RESPONSES IN THE RAT AORTA

1. Acetylcholine often fails to induce endothelium-dependent relaxatio n in human vessels in vitro. Due to the fact that most of these vessel s come from surgery, we examined the influence of drugs used in anesth esia on endothelium-dependent responses in rat aorta. 2. Groups of mal e Wistar rats of the following treatments were utilized: P group, diaz epam + promethazine + atropine; I group, pentothal + succinylcholine; IG group, halothane + nitrous oxide; M group, morphine + pancuronium; C group, untreated rats. Dose-response curves to noradrenaline and ace tylcholine were determined in rat aorta in vitro, in the presence and absence of endothelium. 3. Acetylcholine induced more relaxation (P < 0.05) in the rat aorta of IG group compared with that of the C group. 4. In the rat aorta from P and IG groups, the contractions produced by several concentrations of noradrenaline were significantly smaller (P < 0.05) when the endothelium was removed. Similar effects occurred in aorta strips of animals previously treated with either atropine, prom ethazine, cimetidine or halothane. 5. Our results suggest that drugs c urrently used in anesthesia interfere with some endothelium-dependent effects on isolated rat aorta but according to these results they do n ot seem to be responsible for the lack of acetylcholine relaxation som etimes described in human vessels in vitro.