Effects of adenosine agonists and antagonists on pulmonary ventilation in conscious rats

1. The effects of intravenous injections of adenosine agonists and antagonists on pulmonary ventilation were investigated in conscious male Sprague-Dawley rats. 2. Adenosine agonists reduced pulmonary ventilation, whereas an adenosine antagonist increased pulmonary ventilation. 3. The adenosine-induced decrease in ventilation could be partially blocked by pretreatment with either an adenosine or opioid antagonist and completely blocked by a combined pretreatment with adenosine and opioid antagonists. 4. Thus, endogenous adenosine appears to have an inhibitory role in the control of pulmonary ventilation in conscious rats, and the mechanism of action appears to involve both adenosine and opioid receptors.