SUPPRESSION BY GABA(B) RECEPTORS OF 4-AMINOPYRIDINE-INDUCED HYPERACTIVITY IN GUINEA-PIG DENTATE NEURONS

Double intracellular recording from granule cells and hilar neurons wa s performed in hippocampal slices to study the effect of gamma-aminobu tyric acid (GABA) receptor antagonists on the activity induced by the convulsant 4-aminopyridine (4-AP) in the dentate gyrus. 4-AP evoked GA BA-mediated responses in granule cells and burst discharges in hilar n eurons. In the presence of GABA(B) but not GABA(A) receptor antagonist s, 4-AP evoked discharge activity in dentate granule cells. When both GABA(A) and GABA(B) receptors were blocked 4-AP induced synchronous 'p aroxysmal depolarizing shift'-like activity in granule cells and hilar neurons. Our data indicate that GABA(B) receptor-mediated mechanisms protect dentate cells against the convulsant effects of 4-AP.