The Effect Of L-NAME On Responses Due To ACh, ATP And NA in Rabbit Thorack Aorta

in the pı-esent study, the ejfects of IVG-nitro L-arginin nıethyl ester (L-NAME), a nitric oxide (NO) synthesis inhibitor. on the contraction due to noradrenaline (NA) and on the inhibition of the NA-induced contractik responses by acetylcholine (ACh) and adenozine 5-triphosphat (ATP) have been investigated in rahhit thoracic aorta with ot- without endothelium. 10-5 M NA-induced contractile responses in tissues with or without endothelium and in the tissue with endothelium, the inhihition of these contraction was found 77.42±6.29 % and 65.76±8.06 %, respectively by addition of cumulative concentration (10-9 - 10-4M) of ACh and ATP. In the presence of L-NAME, the inhibition due to of these agents was found as 28.37±2.5 % and 21 .56±2.55 % respectively. While any inhibition due to ACh does not occur in the tissue without endothelium ATP inhibited the reponses of NA at the rate of 23.17±2,61 % and addition of L-NAME to the mediurn did not change the responses. In another pan, in the tissue with endotheliunı the NA (10-9 - 104M) induced contractik responses was found 131 .56±8.43 % in the presence of L-NAME (10-6M) Whereas there's no effect due ta L-NAME in the tissue without endothelium. It has alsa been reported that L-NAME has no effects on the hasat tension, in this study. The ı-esults suggested that, an itact endothelium is essential for the inhihition of the muscle contraction with ACh in tissues ıısed. Morover alsa found that ATP-relıvcations vı'ere free from endothelium, in addition that L-NAME inhihits NO-mecliated relaxations due ta hoth agents in endothelial tissues and increased the contractions due ta NA, too.