Propofol-induced relaxation of rat aorta is altered by aging

Background : Propofol causes vasodilation via endothelium-dependent and -in- dependent mechanisms. Because endothelial function is impaired with aging, the effects of propofol on endothelium-dependent vasodilation might be altered by aging. The aim of this study was thus to determine the effects of aging on vascular responses to propofol. Methods :Y oung (4-6 weeks old) or adult (16-25 weeks old) rats were anesthetized with sevoflurane. The thoracic aorta was dissected and cut into pieces 3-4 mm in length. In some rings, the endothelium was deliberately removed. The ring segment of the aorta was mounted for isometric force recording at a resting tension of 0.5-1.0 g in a 2 ml organ bath, containing Krebs-Ringer bicarbonate buffer. Arteries were precontracted with phen- ylephrine, and the function of endothelium was confirmed with acetylcholine. Then, we studied the concentration-dependent effects of propofol in endothelium-intact (control group) and -denuded aortic rings (denuded group), as well as those treated with N ω -nitro- L-arginine methylester (L-NAME group). Results : Relaxation due to propofol was ob- served in the control groups of both young and adult rats in a concentration-dependent manner, but the magnitude of relaxation was significantly greater in young rats. In addi- tion, in young rats, relaxation due to propofol was significantly and equally reduced in both L-NAME and denuded groups at all propofol concentrations that we studied (10 -6 - 10 -3 M). In adult rats, relaxation due to propofol was quite similar between control and L- NAME groups at all propofol concentrations, whereas it was significantly reduced in the denuded group. Conclusion : These results suggest that endothelium-derived nitric oxide plays an important role in propofol-induced vasodilation in young rats, but not in adult rats. J. Med. Invest. 61 : 278-284, August, 2014