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 (0.05-0.1mg ICV) administration. f/min, VT ,VE and BP increased significantly during hypoxic gas mixture breathing before dipyridamole administration in intact rabbits (p < 0.01, 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 normoxia 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.