백서의 적출된 기도평활근에서 Ketamine의 이완효과 = The relaxant effect of ketamine on the rat-airway smooth muscle

다국어 초록 (Multilingual Abstract)

The effects of anesthetics on airway smooth muscle tone are important in the management of patients with asthma. Airway epithelial cells and vascular endothelial cells modulate the tone of the underlying smooth muscle by releasing relaxing factors such as prostanoids and nitric oxide (NO). Ketamine, at concentrations achieved with the usual clinical doses, has a direct relaxant effect on airway smooth muscle. In the present study we evaluated whether the relaxant effect of ketamine depend on any of the epithelium-derived relaxing factors. Isolated rat tracheal preparations mounted in water-jacketed organ baths filled with modified Tris Tyrode buffer solution with 100% oxygen at 37˚C for recording isometric contractile force. In the first experimental step, Tracheae, in the absence and in the presence of epithelium, were contracted with acetylcholine(10^-8M-10^-3M), and we plotted concentration -response curve for the Ach. And then we examined the inhibitory effect of ketamine(10^-5 and 10^-4M) on the concentration-response curve for Ach. In the second experimental steps, we studied the effect of N-omega-nitro L-arginine methylester(L-NAME) on the relaxant activity of ketamine(10^-6-10^-3M) on trachea contracted by 10^-5M Ach. In the result, 1) Removal of the tracheal epithelium did not change the response to Ach. 2) 10^-5M ketamine not significantly changed, but 10^-4 M ketamine shifted to the right the concentration-response curves for Ach in both intact and denuded epithelium rings. 3) L-NAME did not influence the relaxant effect of ketamine on trachea contracted by 10^-5 M Ach.
These results indicate that ketamine-induced tracheal smooth muscle relaxation is epithelium-independent and may be is mediated by inhibition of Ca^++ influx in nonspecific way.