Adenosine receptor antagonism accounts for the seizure-prolonging effects of aminophylline.

The mechanism of action of aminophylline in prolonging seizures was tested in amygdala-kindled rats. Aminophylline prolonged the afterdischarge duration of kindled seizures. This seizure-prolonging action of aminophylline was strongly antagonized by the adenosine A1 agonist cyclohexyladenosine and partially antagonized by the benzodiazepine partial agonist RO 15-1788. However, the specific benzodiazepine antagonist CGS 8216 did not affect the seizure-prolonging action of aminophylline. Also, the potent anticonvulsant effect of diazepam on kindled seizures, which was completely antagonized by CGS 8216, was unaffected by aminophylline. Furthermore, a range of benzodiazepine inverse agonists, GABA antagonists, phosphodiesterase inhibitors and xanthines did not prolong afterdischarge durations. These results demonstrate that the seizure-prolonging action of aminophylline is due to block of A1 adenosine receptors since it is prevented by adenosine A1 agonists.