[PLASTIC REORGANIZATION OF THE ULTRASTRUCTURE OF SYNAPSES IN THE CEREBELLUM DUE TO TOXIC EFFECTS OF GLUTAMATE AND NO-GENERATING COMPOUND].

Ultrastructural changes in synapses between parallel fibers (PF) and the spines of Purkinje cell dendrites (PCD) in frog cerebellum were studied after exposure to high concentrations (1 mM) of glutamate (Glu) and NO-generating compound in experimental model. It was shown that exposure to Glu resulted in the envelopment of the terminal bouton by the spine, while under the influence of NO-generating compound, on the contrary, the spine was surrounded by the bouton. Morphological study has shown that in Glu solution there was the predominance of synapses in which the glial cells surrounded the spines, while in the presence of NO they covered the boutons. After the electrical stimulation of PF, the relative number of synapses, containing the boutons surrounded by glial cells, was 10 times higher as compared to those in which the glial cells surrounded the spines. The observed morphological changes reflect the functional state of synapses between PF and PCD in response to the damaging effects of excess Glu and NO, that is expressed in different forms of synaptic contacts and neuronglial structures.