[Desmosome-like contacts of Mauthner neurons as targets of scorpion venom].

Desmosome-like contacts (DLC) in afferent chemical synapses of the Mauthner cells (MC) were investigated after application of low and high molecular mass peptide fractions 6 and 9, correspondingly, from the Central Asiatic black scorpion Orthochirus scrobiculosus. Besides, the DLC were examined in condition of a training induced morpho-functional stability of the MC (adaptation) mediated by transformation of actin monomers into polymers. In addition, the structure of DLC was studied after cytochalasin application which disrupts F-actin. Fraction 6 was shown to increase the length of DLC and osmiophily of fibrous material. Similar changes in DLC were caused by adaptation. Fraction 9 decreased the osmiophily of the fibrous material, made DLC asymmetric, but did not influence their length. Similar changes in DLC were seen also after cytochalasin D application. Taking into account our previous data on the role of F-actin in the MC functioning, which were obtained following specific pharmacological treatments, the similarity of ultrastructural changes in DLC after both adaptation and fraction 6 application, on the one hand, and after both cytochalasin D and fraction 9 application, on the other one, enabled us to suggest that these fractions may contain peptides able to exert influence of the actin cytoskeleton.