Immunohistochemical evidence of the presence of metabotropic receptors for γ-aminobutyric acid at the rat neuromuscular junctions.

in the synapses of the "fast" (m. EDL) and "slow" (m. soleus) skeletal muscles of the rat GABABR1 and GABABR2 subunits of metabotropic receptors for γ-aminobutyric acid (GABA), located primarily on the motor nerve ending membrane were detected by immunohistochemistry and fluorescence microscopy methods.

[Non-quantal mediator release: myth or reality?].

In the present review we analyze the papers devoted to phenomenon of non-quantal mediator release from the modern concepts of the functioning of synaptic contacts. In this connection the conception of quantal mediator release by itself is discussed as well as the mechanisms underlying the both the quantal and the non-quantal modes of signal molecules secretion. The data are systematized which verify the existence of the non-quantal mode of signaling in different synapses and demonstrate its physiological role.

Posttraumatic survival of sensory neurons during allotransplantation of rat embryonic tissues into the nerve.

Allotransplantation of the liver, hindlimb, and bone marrow tissues from 14-day-old embryos into the sciatic nerve had a modulatory effect on survival of various populations of axotomized neurons in L5 spinal ganglion in an adult rat.

Effect of dipeptide N-acetylaspartylglutamate on denervation-induced changes in the volume of rat skeletal muscle fibers.

N-acetylaspartylglutamate prevents the denervation-induced increase in the volume of muscle fibers in rat diaphragm, the phenomenon being more pronounced for the hydrolysable isomer. The effect of dipeptide manifested against the background of blockade of metabotropic glutamate receptors. It was hypothesized that N-acetylaspartylglutamate is involved in the regulation of the volume of skeletal muscle fibers via activation of ionotropic receptors by both dipeptide and glutamate molecules.

[Glutamatergic modulation of vertebrate neuromuscular transmission]. / Gluitamatérgicheskaia moduliatsiia nervno-myshechnoi peredachi u pozvonochnykh.

The paper is devoted to the analysis of evidence pointing to presence of glutamatergic modulation of vertebrate neuromuscular transmission. The data on the glutamate's origin and release in the endplate region as well as on the presence of specific glutamate receptors are discussed. The effects of glutamate on different types of acetylcholine secretion in the synapses of amphibians and mammals are described. The question of possible physiological role of glutamatergic modulation of neuromuscular transmission is discussed.

Effect of oxotremorine on resting membrane potential and cell volume in skeletal muscle fibers in rats after in vivo blockade of NO-synthase.

Denervation of rat phrenic muscle or block of NO-synthase in vivo increased the cross-section area of muscle fibers and decreased membrane resting potential. Oxotremorine prevented the development of denervation-induced or denervation-like (i.e. induced by NO-synthase blockade) membrane depolarization and increase of the cross-sectional area of muscle fibers. Pirenzepine abolished the effects of oxotremorine. It was concluded that non-quantal acetylcholine can be involved in the regulation of skeletal muscle fiber volume via activation of M1 muscarinic receptors followed by NO synthesis.

The effects of glutamate on spontaneous acetylcholine secretion processes in the rat neuromuscular synapse.

Experiments on rat diaphragm muscles showed that glutamate (10 microM-1 mM) had no effect on the mean frequency, interspike intervals, and amplitude-time characteristics of miniature endplate potentials, but had a suppressive action on non-quantum secretion (the intensity of which was assessed in terms of the H effect). The effect of glutamate was markedly concentration-dependent and was completely overcome by blockade of NMDA receptors, inhibition of NO synthase, and by binding of NO molecules in the extracellular space by hemoglobin. It is suggested that glutamate can modulate the non-quantum release of acetylcholine, initiating the synthesis of NO molecules in muscle fibers via activation of NMDA receptors followed by the retrograde action of NO on nerve terminals.

[Pharmacological parameters of muscarinic cholinoreceptors in skeletal muscles]. / Farmakologicheskie osobennosti muskarinovykh cholinoretseptorov skeletnykh myshts.

It has been shown that bath application of muscarine delayed the early post-denervation depolarization in the muscle fibers incubated for 3 h in culture medium. The greatest reduction of the post-devervation depolarization was observed with 50 nmol/l muscarine. Atropine, a muscarinic antagonist, clozapine, a specific inhibitor of M1/M5-cholinergic receptors, and nitrocaramiphen, a M1-antagonist, completely removed the hyperpolarizing effect of muscarine. 4-DAMP, a specific inhibitor of M3-cholinergic receptors, himbacine, an antagonist of M2-cholinergic receptors, and tropicamide, a specific inhibitor of M2/M4-cholinergic receptors, failed to prevent the effect of muscarine. A M1/M2 muscarine agonists propargyl and but-2-ynyl esters of arecaidine had apparent muscarine-like effect. Nitrocaramiphen, and not himbacine, prevented the hyperpolarizing effect of these cholinomimetics. It is concluded that muscarine and esters of arecaidine delay the development of early postdenervation depolarization in M1-cholinergic receptors of skeletal muscle.

[Effect of glutamate on membrane potential and volume of the skeletal muscle fibers in rats following NO-synthase inhibition in vivo]. / Vliianie glutamata na membrannyi potentsial i ob''em skeletnykh myshechnykh volokon krysy posle blokady NO-sintazy in vivo.

Cross-sectional area (CSA) of muscle fibers incubated in culture medium 199 for 3 hours dramatically increases, whereas resting membrane potential (RMP) decreases compared to "freshly-isolated" muscles. Both glutamate and sodium nitroprusside prevent these changes. MK-801, a specific inhibitor of NMDA-receptors, eliminates protective effects of glutamate on both CSA and RMP. NO-synthase inhibition in vivo promotes an increase of initial CSA and decrease of mean RMP. Under these conditions, effects of glutamate and sodium nitroprusside on CSA and RMP of denervated muscles are less obvious. It has been concluded that synaptic glutamate is able to participate in regulation of RMP and cell volume in muscle fibers through the activation of postsynaptic NMDA-receptors and muscle NO-synthase.

[Effect of glutamate on spontaneous secretion of acetylcholine in the nerve-muscle synapse in rats]. / Vliianie glutamata na protsessy spontannoi sekretsii atsetilkholina v nervno-myshechnom sinapse krysy.

In rats, glutamate was shown to exert no effect on the mean frequency, character of interstimuli distribution, amplitude and temporal parameters of the miniature EPPs. Glutamate suppressed nonquantal release. The glutamate effect depended on its concentration and was abolished by blockade of NMDA receptors, NO-synthase inhibitoin, and NO molecules binding by haemoglobin in extracellular medium. Glutamate seems to modulate the nonquantal acetylcholine secretion by initiation of the NO synthesis in muscle fibres via activation of the NMDA receptors.