A long-term incubation of the goldfish hindbrain stumps with the mauthner cells is accompanied by changes of specialized contact dimensions of afferent mixed synapses

摘要

Dimensions of specialized contacts (active zones, AZ; puncta adhaerentia, PA; and gap junctions, GJ) were investigated at afferent mixed synapses, which arc axonal endings of the 8th nerve roots on M-cell distal parts of lateral dendrites, in the intact stumps of the goldfish medulla oblongata and in those incubated for a long time. It was shown that during the incubation the length of mixed synaptic apposition profile decreased by 24 %. The length of individual profile of GJ, PA and AZ became shorter by 10, 43, and 18 %, resp. The total length of PA within the. mean synaptic apposition profile decreased by 44 %. The proportion of synaptic apposition occupied by PA decreased by 22 %, and that of GJ increased by 45 %. The number of specialized contacts per apposition did not change. Thus, PA and GJ at afferent mixed synapses changed drastically in consequence of a prolonged incubation of M-cells in vitro. It is supposed that the realignment of these structures, the former of which is known to consist of actin, and the latter is presumably under the control of, his cytoskeletal protein, occurs due to some adaptive reaction to changes in the internal milieu. This in turn may presumably be related to the injure of M-cells during the isolation of the brain, and to the influence of survival in artificial medium affecting the state of neuronal actin.