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 sync hronization of burst discharges in hilar neurons was studied using pai red intracellular recording from hilar neurons and granule cells of gu inea pig hippocampal slices. The convulsant 4-aminopyridine (4-AP, 50- 100 mu M) induced synchronous burst discharges in hilar neurons time l ocked to giant inhibitory postsynaptic potentials (IPSPs) in granule c ells. 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 smal ler in the presence of CNQX than in its absence. We conclude that glut amatergic synapses operating through non-NMDA receptors are required f or the synchronization but not for the generation of burst discharges which are induced by 4-AP in hilar neurons.