Role of adenosine in the hypoxic ventilatory response of the newborn piglet

The role of intracerebral adenosine levels in the control of ventilatory response to hypoxia was explored in 15 spontaneously breathing intubated piglets, 1–5 days old, sedated with chloral hydrate. Respiration was recorded via by a pneumotachograph. In all animals exposed to hypoxia (12% 0₂) for 10 minutes. There was an initial increase in ventilation followed by a late decrease (the biphasic ventilatory response). Both intravenous caffeine citrate (20 mg/kg) and an Fi_ico of 0.05 separately abolished or attenuated the late ventilatory depression associated with hypoxia. In the same piglets, the administration of 10 pg dipyridamole, a competitive inhibitor of adenosine receptors, directly into the cerebral ventricles abolished the hyperventilatory response to hypoxia. Conversely, the use of 20 μg intraventricular 8‐phenyltheophylline abolished the late ventilatory depression associated with hypoxia. Neither drug had a direct effect on ventilation at the time of injection. These results suggest that adenosine is a part of the diphasic ventilatory response to hypoxia. Pediatr Pulmonol. 1994; 17:50–55. © 1994 Wiley‐Liss, Inc.