[Changes in molluscan neurons under the influence of proteolytic enzymes]

The goal of the work was to study the structure of neurons treated with proteases and to elucidate if this could lead to the formation of the interneuronal syncytial connections. In the first series of experiments, phase contrast observation of the living dissociated ganglionic neurons of the mollusc Lymnaea stagnalis treated with 0.4% pronase, demonstrated a retraction of nerve processes and a two-phase change of the cell body volume. At the first stage, the soma volume decreased, on the average, for 82.5 min by 12.1%; subsequently, the volume increased, on average, by 14.1%. Signs of neuronal vital activity in Ringer's solution were observed, on the average, for 828 min, while in pronase solution their duration was 1.4 times shorter. In the second series of experiments, the study of neuronal ultrastructure has demonstrated in many cases the integrity of mitochondria, rough and smooth endoplasmic reticulum (ER), Golgi complex, light and granular vesicles, nuclear structure, and the preservation of the optical density of neuroplasm. The cells making contacts after centrifugation form uniform intercellular clefts of about 20 nm. Point approaches of membranes were very rare. No signs of syncytial connections were detected. Elongation and fusion of smooth ER cisterns separated the fragments of soma from relatively undamaged cells. Some neurons were damaged, they contained numerous vacuoles formed by swollen mitochondria and ER cisterns. The nerve process fragments, detached during the dissociation, were surrounded by the normal plasma membrane.