[Protective function of sigma-1 receptor in spinal cord motor neurons].

Sigma-1 receptor plays a protective function in various tissues. It was shown recently that a mutation in the sigma-1 receptor results in appearance of Amyotrophic Lateral Sclerosis (ALS). In the central nervous system (CNS) the highest amounts of sigma-1 receptor are found in motoneurons of the spinal cord, where receptor is localized in subsurface cisternae of cholinergic postsynaptic densities. The sigma-1 receptor is thought to regulate the ion channels activity and thus may influence neuron excitability. In this review we consider the possible pathways by which the sigma-1 receptor may reduce the excitability of motoneurons and thereby play a protective function during the progression of ALS.

[Calcium ions distribution in mixed synapses of the mauthner neurons of goldfish in the norm, fatigue, and adaptation state]. / Raspredelenie ionov kal'tsiia v smeshannykh sinapsakh mautnerovskikh neironov zolotoi rybki v norme, pri utomlenii i pri adaptatsii k nemu.

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.

[Morpho-functional changes of Mauthner neurons after treatment with neuropeptide kyotorphin ]. / Morfofunktsional'nye izmeneniia mautnerovskikh neironov pri vozdeistvii neiropeptida kiotorfina.

Influence of neuropeptide kyotorphin (L-thyrosyl-L-arginine) treatment on goldfish Mauthner cells was studied separately or in combination with prolonged natural stimulation of these neurons. The neuroprotective effect of this substance at both functional and ultrastructural levels was demonstrated. Possible mechanisms of kyotorphin action is discussed with regard to its modulating effect on intracellular calcium ion concentration.

[Ultrastructural localization of calcium pyroantimonate in Mauthner neurons of goldfish fry adapted to natural stimulation]. / Ul'trastrukturnaia lokalizatsiia piroantimonata kal'tsiia v mautnerovskikh neironakh mal'kov zolotoi rybki, adaptirovannykh k estestvennoi stimuliatsii.

The localization of Ca2+ in control and adapted goldfish fry Mauthner cells (M-cells) revealed by sedimentation with potassium pyroantimonate technique was investigated. It has been shown the following. 1. In the control M-cells electron dense precipitates are present in the extracellular space, commonly within the active zone clefts of chemical synapses, throughout the whole apposition of the mixed synapses and in the synaptoplasm of both type afferent boutons. No precipitates were seen in the cytoplasm of M-cells. 2. After long term natural (vestibular) stimulation (LTNS), resulting in a strong functional suppression of M-cells, precipitates disappeared entirely from active zones but remained numerous in the cytoplasm of M-cells. The distribution of precipitates within the cytoplasm was non-uniform, the highest density was observed on the surfaces of intracellular organelles and elements of the cytoskeleton. 3. In fatigued M-cells after LTNS and after a subsequent one day rest the distribution of precipitates was less intensive, while in the whole it resembled that of fatigued M-cells. 4. In adapted M-cells the distribution of precipitates was similar to that observed in control. M-cells after LTNS, but the amount and size of the precipitated grains were noticeably increased. 5. The most numerous precipitates were seen in adapted M-cells after LTNS. They were localized throughout the postsynaptic cytoplasm and in a lesser order in the presynaptic cytoplasm. 6. After one day rehabilitation the intensitivity of cytochemical reaction of Ca2+ ion precipitation restored to the initial stage characteristic of adapted M-cells before LTVS. The results obtained suggest that the total concentration of Ca2+ ions in adapted M-cells and the dynamics of their exchanges between cytosole and intracellular depots, such as the smooth endoplasmic reticulum, may increase to keep a normal or even increased functional activity of M-cells, both before and after the LTNS.

[Features of morphofunctional rehabilitation of Mauthner neurons after fatigue]. / Osobennosti morfofunktsional'noi reabilitatsii mautnerovskikh neironov posle utomleniia.

Structural reorganization of smooth endoplasmic reticulum (SER) in relation to changes in functional state of neurons has been investigated using fatigue and subsequent rhabilitation of the goldfish Mauthner (M-) cells as experimental approach. The recovery of original structure of SER in distal parts of dendrities after its significant proliferation, caused by a 3 h natural stimulation, markedly retarded, as compared with quickly normalized functional activity of M-cells. At the same time in somata and proximal parts of dendrites the structural recovery of SER coincided with restoration of the initial function of M-cells. The results suggest that within a single neuron SER with its obvious structural plastisity the neuron functional activoty is supported and restored through regulating the extent of proliferation angmenting Ca(2+)-accumulation in its compartments. Nevertheless SER posseses certain autonomy in structural recovery within somata and dendrites. Such differences of SER plasticity in different parts of the same neuron presumable reflect differences in interaction of its individual compartments with the cytoskeleton and adjacent cytoplasm, or may be caused by different activity of synapses situated on the soma and dendrites.