Gülderen ŞAHİN, Rıfat YÜCEL, Tülin ORUÇ, İbrahim GÜNER, Karaturan Nermin YELMEN

Endojen adenozin’in santral solunum kontrol mekanizmalarına etkisi

Çalışmamızda Na-pentobarbital (25 mg/kg i.v) ile anesteziye edilen intakt (Periferik kimoreseptörleri sağlam) ve periferik kimoreseptörleri denerve tavşanlar kullanıldı. Her iki grup tavşanda sol lateral ventrikül içine adenozin geri-alım inhibitörü olan dipyridamole (0.05-0.1 mg) yan ventrikül içine intraserebroventriküler (ICV) uygulanarak, endojen adenozinin'in santral solunum kontrol mekanizmalarına ve hipoksiye karşı oluşan solunumsal cevaba etkisi incelendi. İntakt ve kimodenerve grup tavşanlara, ICV dipyridamole uygulanması öncesinde ve sonrasında, gerek hava (normoksi) gerek¬se hipoksik gaz karışımı (% 8 O2 - % 92 N2) solutulmasında soluk hacmi (VT), solunum frekansı (f/dk.) ve sistemik arteriyel basınç (SAB) poligrafta kaydedildi. Vrve f/dk. değerlerinden solunum dakika hacmi (VE) hesaplandı. İntakt grup tavşanlara hipoksik gaz karışımı solutulması f/dk., V-r, VE ve SAB'da anlamlı artışlar oluşturdu (p < 0.01, p < 0.05, p < 0.05, p < 0.001). ICV dipyridamole verilmesi ise, VT ve VE'de anlamlı artışlar meydana getirirken (p < 0.05, p < 0.05), f/dk.'da anlamsız bir azalma oluşturdu. SAB'da ise anlamlı bir azalma gözlendi (p < 0.05). Periferik kimodenerve tavşanlara hipoksik gaz karışımı solutulmasında f/dk., VT, VE ve SAB'da anlamlı azalmalar gözlendi (p < 0.01, p < 0.001, p < 0.001, p < 0.001). ICV dipyridamole ise VT, VE veSAB'ı anlamlı olarak azaltırken (p < 0.01, p < 0.05, p < 0.001), f/dk.'da anlamsız bir artış oluşturdu. Dipyridamole ile birlikte hipoksi uygulanmasında benzer bulgular elde edildi. Sonuç olarak bulgularımız, beyinde dipyridamole ile oluşturulan endojen adenozin'in, ventilasyona olan santral etkilerinin, hipoksinin direkt merkezsel etkilerine benzer şekilde, inhibitor nitelikte olduğunu göstermektedir.

Effect of endogenous adenosine on central respiratory control mechanisms

In this study the effect of endogen adenosine on central respiratory control mechanisms and hypoxic ventilatory responses was investigated. For this purpose dipyridamole, an adenosine reuptake inhibitor was injected into left lateral cerebral ventricle (ICV) of anesthetized (Na-pentobarbital 25 mg/kg i.v) peripheral chemoreceptors intact and chemodenervated rabbits. Systemic arterial blood pressure (BP), tidal volume (VT) and respiratory frequency (f/min) were recorded while the animals were breathing air or hypoxic gas mixture (8 % O2 - 92 % N2) before and after dipyridamole (0.05-0.1 mg ICV) administration, f/min, VT ,VE and BP increased significantly during hypoxic gas mixture breathing before dipyridamole administration in intact rabbits (p < 0.0'1, p < 0.05, p < 0.05, p < 0.001). When dipyridamole was administered (ICV) during air breathing VT and VE increased significantly (p < 0.05, p < 0.05) while no significant decreases was observed in f/min. BP decreased significantly (p < 0.05). On the breathing of hypoxic gas mixture before dipyridamole administration of chemodenervated rabbits, the decreases in f/min,VT ,VE and BP were founded significantly (p < 0.01, p < 0.001, p < 0.001, p < 0.001). ICV administration of dipyridamole during 'Rormoxia caused significant decreases in VT, VE and BP (p < 0.01, p < 0.05 p < 0.001) while no significant change was observed in f/min. Comparable findings were obtained when dipyridamole was administered during hypoxic gas mixture breathing. The results of this study show that augmentation of endogenous adenosine in brain with dipyridamole produces a direct inhibitory effect on central respiratory control mechanisms similar to that of hypoxia.

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