[Contraction of the injured neuronal processes]

The investigation was performed on the isolated living neurons of a mollusk (Lymnaea stagnalis). The purpose of this study was to examine the contractile activity of the injured neuronal processes. Retraction of latter in Ringer's solution was found in 90% of the cases. The specific club-shaped structure (retraction bulb) served as a marker of contraction. The speed of process contraction fluctuated in different neurons from 0.03 to 9 microm/ min. As a result of usual linear contraction, the process diameter was increased on the average by 35%, while the cell body volume was increased on the average by 30%. The three forms of contractile activity were distinguished: linear contraction, isometric contraction (reduction of a process thickness with no change in its length) and mixed form of contraction. It is suggested that the mechanism of retraction takes part in the formation of diastasis after nerve sectioning and injury of the brain conducting pathways. Diastasis in the nerve is formed not only due to the elastic properties of its fibrous sheath and glia, but also as a result of nerve fiber retraction.