RESUMO
Electron microscopical and electrophysiological studies were carried out in cross-sections of the hippocampus of 4-weeks-old male rat pups (n = 35) to detect the ultrastructural changes in CA1 hippocampal area and the peculiarities of excitatory postsynaptic potential formation in this brain area after the incubation of the sections in the solution of hyaluronidase (10 U/ml), the enzyme which specifically degrades the extracellular matrix glycosaminoglycan--the hyaluronic acid. The reduction of the width of synaptic cleft by 15-25% in the axo-dendritic contacts of the stratum radiatum of CA1 hippocampal area was detected 1.5 min following the application of enzyme, coinciding with the increase of the excitatory postsynaptic potential amplitude. The width of synaptic cleft was further reduced by 45-55% after 4.5 min of incubation; during this period the blockade of signal transmission along the Schaffer's collaterals to CA1 hippocampal area was observed. Thus, the structural and functional state of glycosaminoglycans is one of the factors controlling the efficiency of synaptic transmission in the brain.