ROLE OF GLUTAMATERGIC SYNAPTIC TRANSMISSION IN SYNCHRONIZED DISCHARGES OF HILAR NEURONS IN GUINEA-PIG HIPPOCAMPAL SLICES

The role of glutamatergic excitatory synaptic transmission in the synchronization of burst discharges in hilar neurons was studied using paired intracellular recording from hilar neurons and granule cells of guinea pig hippocampal slices. The convulsant 4-aminopyridine (4-AP, 50-100 mu M) induced synchronous burst discharges in hilar neurons time locked to giant inhibitory postsynaptic potentials (IPSPs) in granule cells. The non-N-methyl-D-aspartic acid (non-NMDA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 5-10 mu M) disrupted this synchrony. The inhibitory effect of gamma-aminobutyric acid (GABA)(B) receptor stimulation on the frequency of synchronous activity was smaller in the presence of CNQX than in its absence. We conclude that glutamatergic synapses operating through non-NMDA receptors are required for the synchronization but not for the generation of burst discharges which are induced by 4-AP in hilar neurons.