Influence of theophylline on concentrations of cyclic 3',5'-adenosine monophosphate and cyclic 3',5'-guanosine monophosphate of rat brain.

The influence of theophylline (2.5--100 mg/kg p.o.) on cyclic 3',5'-adenosine monophosphate (cAMP) and cyclic 3',5'-guanosine monophosphate (cGMP) in brain of Sprague-Dawley rats (0.5--3.0 hr after administration of theophylline) was investigated. It was found that theophylline increases cAMP and cGMP levels when administered in a dose of 25 mg/kg or higher. A significant decrease of cGMP level was observed after administration of 10 mg/kg. The results of this study suggest that the influence of theophylline on cyclic nucleotide levels of rat brain is the result of two factors: (a) inhibitory properties of theophylline on cAMP and cGMP phosphodiesterases and (b) competition of theophylline with adenosine.