[Effect of acetylcholine on the ultrastructure of interneuronal synapses]

Effect of 10(-4) M solution of chlorous acetylcholine (ACh) on ultrastructure of the leech (Hirudo medicinalis) cerebral synapses has been studied. ACh can produce an increased adhesion in membranes of the neuropil, nearly similar to that observed at its electrostimulation. The main manifestations of the increased membrane adhesion are: association of the electron opaque substance on the surface of organelles and in the submembrane layer, aggregation of synaptic vesicles, their adhesion with mitochondria, aggregation of the electron opaque material on the external surface of plasmalemmas (in intercellular clefts) and formation of glio-neuronal contacts. Variousness of the effects mentioned and participation of different membrane types in them demonstrate that the increased adhesion a reaction is not specific. Not only membrane (lipid-containing) structures participate in it, but also a structural matrix of cytoplasm and submembrane layer, the bases of the latter make certain proteins. It is possible to think that the leading mechanism of the adhesive changes mentioned is the reaction of membrane and cytoplasmic proteins. This coordinates with the data of previously performed intravital direct ultraviolet cytospectrophotometric and interferometric investigations.