Suppression by GABAB receptors of 4-aminopyridine-induced hyperactivity in guinea-pig dentate neurons

Double intracellular recording from granule cells and hilar neurons was performed in hippocampal slices to study the effect of gamma-aminobutyric acid (GABA) receptor antagonists on the activity induced by the convulsant 4-aminopyridine (4-AP) in the dentate gyrus. 4-AP evoked GABA-mediated responses in granule cells and burst discharges in hilar neurons. In the presence of GABAB but not GABAA receptor antagonists, 4-AP evoked discharge activity in dentate granule cells. When both GABAA and GABAB receptors were blocked 4-AP induced synchronous 'paroxysmal depolarizing shift'-like activity in granule cells and hilar neurons. Our data indicate that GABAB receptor-mediated mechanisms protect dentate cells against the convulsant effects of 4-AP.