Solunumun adenozin ile baskılanmasında hiperkapniye karşı solunumsal cevabın incelenmesi

Respiratory response to hypercapnia during depression of respiration by adenosine

Özet

İnsanda ve deney hayvanlarında gerek izokapnik gerekse polikilokapnik uzun süreli hipoksiye karşı solunumsal cevap bifaziktir. Ventilasyonda ilk 5 dakika artış, sonra azalma meydana gelir. Hipoksik depresyon adı verilen ventilasyondaki azalmadan beyinde biriken Adenozin sorumlu tutulmuştur: Bu çalışmada anestezi altındaki (pentotal-Na- 30 mg/kg İ.P.) kemodenerve vagotomize 6 kedide intraserebroventriküler (i.c.v.) Adenozin (100-120 ug/kg i.c.v.) uygulaması ile oluşturulan solunum depresyonunda hiperkapniye karşl solunumsal cevap soluk hacmi (VT) ve soluk frekansı (f) kaydedilerek incelendi. Solunum dakika hacmi (VE) hesaplandı. Adenozin uygulamasından önce hiperkapnik gaz karışımı (%5,8 CO2-Hava) solutulmasında VT'nin ve VE'nin anlamlı (p

Abstract

Background and Design.- Ventilatory response to sustained (>30 minutes) hypoxia is biphasic in humans and experimental animals. A brisk initial increase in ventilation is followed by a decline that is thought to be of central origin and has been termed "hypoxic depression". Results of several studies have suggested that concentration of adenosine within the brain increases as a result of hypoxemia and adenosine could therefore play a key role in mediation of hypoxic depression. The purpose of the present study was to produce a state of inhibition in the respiratory centers by adenosine administration (i.c.v.) and to examine the respiratory response to hypercapnia. The experiments were carried out in six peripheral chemodenervated vagatomized cats under pentothal anesthesia. For i.c.v. injections of adenosine in each animal, canula was placed in left lateral cerebral ventricle by stereotaxic method. Animals were allowed to breathe air and hypercapnic (5.8% CO2-air) gas mixtures before and after i.c.v. adenosine administration. Respiratory frequency (f), tidal volume (TV), arterial blood pressure were recorded. Respiratory minute volume (VE) and the mean arterial pressure were calculated. At the end of each experimental phase pO2, pCO2, pH were measured in arterial blood samples. Results.- When chemodenervated vagotomized animals were allowed to breathe the hypercapnic gas mixture before adenosine administration VTand VE increased significantly (p