Cyclic GMP and cyclic AMP in the cerebral cortex of mice during seizures induced by 3-mercaptopropionic acid: effects of anticonvulsant agents.

The onset of clonic seizures induced by 3-mercaptopropionic acid (MP) was associated with an approximately 200% increase of cAMP and a 70% elevation of cGMP in the mouse cerebral cortex. There was a further rise of both nucleotides during the subsequent tonic phase of convulsions; cAMP levels reached 400% and cGMP levels 300% of control values. The levels of both nucleotides did not differ from the controls 20 min after the termination of tonic seizures. When MP convulsions were prevented by Na-phenobarbital, the levels of both nucleotides were not different from control concentrations. Phenytoin prevented the tonic extension, but did not affect the clonic seizures. The accumulation of cAMP was markedly reduced (a residual + 40%), whereas the increased levels of cGMP remained unaffected.