Theophylline has an antagonistic interaction with which of the following receptor?

Theophylline has an antagonistic interaction with adenosine receptors. Adenosine acts as a local mediator in CNS, CVS and other organs, cause contraction of smooth muscles especially bronchial, dilates cerebral blood vessels, depress cardiac pacemaker and inhibits gastric secretion. Methylxanthines acts by antagonizing adenosine receptors resulting in opposite effects. Ref: Essentials of Medical Pharmacology, 5th Edition, Page 203