[Calcium ions distribution in mixed synapses of the mauthner neurons of goldfish in the norm, fatigue, and adaptation state].
The aim of this investigation was to study the structure of giant myelinated club-shaped terminals (afferent mixed synapses) of goldfish Mauthner (M-) cells in different functional states and to demonstrate calcium ion localization in them using modified pyroantimonate method. It was shown that in intact preparations calcium pyroantimonate precipitate was detected neither in gap junctions (GJ) nor in desmosome-like junctions (DLJ). The fibrillar bridges within DLJ cleft were not contrasted. After natural stimulation, which elaborated a long-term adaptation of M-cells, electron dense precipitate was found in GJ, lining all the cleft. Simultaneously fine granules and aggregates of precipitate appeared in DLJ gap and were intensely deposited over the bridges. It is known that the increase of calcium ion concentration up to and above the level demonstrable by pyroantimonate method blocks the electrotonic coupling and that filamentous actin is able to conduct electrotonic signal as a cationic current. Therefore calcium pyroantimonate staining of DLJ bridges, which were earlier shown to contain actin, indicates the association of calcium ions with filamentous actin, i.e. the functioning of bridges as transsynaptic electrotonic shunts at a moment of fixation. The data obtained allow to make a conclusion that DLJ in mixed synapses have not only a known adhesive function, but also a communicative one. The latter is manifested in extreme conditions, thus permitting synapse to maintain or change their conductivity in accordance with environmental demands.
Laboratory of Neuron Ultrastructure, RAS Institute of Theoretical and Experimental Biology, Educational Center of Biophysics and Physiology, Pushchino State University, Pushchino.
D A
DA
Moshkov
E N
EN
Bezgina
L L
LL
Pavlik
N F
NF
Mukhtasimova
T A
TA
Mavliutov
D000222:Adaptation, Physiological; D000818:Animals; D002118:Calcium / Q000032:analysis*; D002413:Cations, Divalent; D006054:Goldfish / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D009411:Nerve Endings / Q000737:chemistry / Q000648:ultrastructure; D009431:Neural Conduction / Q000502:physiology; D009475:Neurons, Afferent / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D013569:Synapses / Q000737:chemistry / Q000648:ultrastructure*; D014722:Vestibule, Labyrinth / Q000502:physiology
D002413:Cations, Divalent; D002118:Calcium