Neirofiziologiia = Neurophysiology最新文献

Advances in modern neuroscience require the identification of principles that connect different levels of experimental analysis, from molecular mechanisms to explanations of cellular functions, then to circuits, and, ultimately, to systems and behavior. Here, we examine how synaptic organization of the sympathetic ganglia may enable them to function as use-dependent amplifiers of preganglionic activity and how the gain of this amplification may be modulated by metabotropic signaling mechanisms. The approach combines a general computational model of ganglionic integration together with experimental tests of the model using the dynamic clamp method. In these experiments, we recorded intracellularly from dissociated bullfrog sympathetic neurons and then mimicked physiological synapses with virtual computer-generated synapses. It thus became possible to analyze the synaptic gain by recording cellular responses to complex patterns of synaptic activity that normally arise in vivo from convergent nicotinic and muscarinic synapses. The results of these studies are significant because they illustrate how gain generated through ganglionic integration may contribute to the feedback control of important autonomic behaviors, in particular to the control of the blood pressure. We dedicate this paper to the memory of Professor Vladimir Skok, whose rich legacy in synaptic physiology helped establish the modern paradigm for connecting multiple levels of analysis in studies of the nervous system.

The crystal structures of glycine, taurine, GABA, beta-alanine were compared. The quantity and the accuracy of distances coincidence between nitrogen and oxygen atoms were used as a criterion of similarity of the crystalline structures. The conclusion is made about a correlation between crystalline structure of agonists and their effect on amino acid receptors. It is assumed that in case of a cooperative effect of agonist on the receptor a mutual arrangement of molecules on the receptor surface is similar to their arrangement in the agonist crystal.

Phosphorylation of the reconstructed TTX-sensitive cytosolic protein of the bovine brain has been studied. Some properties of the protein are similar to those of the membrane potential-dependent sodium channel. It is shown that the influence of phosphorylation by protein kinase A on the reconstructed channel greatly depends on the mode of reconstruction. Phosphorylation fo reconstructed channels in the open state leads to their closing. Preliminary phosphorylation of channel-forming protein results in a considerable increase of the activation effect of veratrine and scorpion toxin.

The structure and topography of carbohydrates on the surface of nerve cells of snail Helix pomatia cultured in vitro have been characterized with a series of colloidal gold-labelled lectins of different sugar specificity. The analysis of the lectin binding has shown substantial differences in the carbohydrate pattern between the soma of monoaminergic and peptidergic neurons. It has been found that the surface of monoaminergic and peptidergic neurons contains N-acetylglucosamine (WGA+) and N-acetyllactosamine (RCA-1-) determinants and does not contain neuraminic acid (LPA-) and complex branched N-glycosyl chains (PVA-). At the same time N-acetylgalactosamine (HPA+) was detected on the peptidergic neuron membrane only. It has been concluded that terminal residues of sialic acid are absent on the most of snail nerve cells. Differences in lectin binding between monoaminergic and peptidergic neurons can serve as a basis for formation of specific connections of cells by different types in the developing brain.

It has been found that smooth muscles play an important role in the mechanism of a sympathetic nervous system effect on the activity of skin receptors. Greater activity of the sympathetic nerve fibres induces higher tension of smooth muscles and thus changes mechanical state of the tissues around the receptors. The latter condition, in its turn, affects the response of receptors to mechanical stimulation. A change in the smooth muscles tension in skin vessels affects the response of receptors to cooling of skin.

Guanosine-5'-triphosphate (GTP)-dependent binding of the agonist D1 dopamine (DA) receptor ligand [H3]-SKF 38393 is described. It is shown that binding of [H3]-SKF 38393 with two different populations takes place in the presence of guanylyl nucleotides, when they are absent--with one population. It is demonstrated using GDP-alpha-P33 binding analysis that the GDP in equilibrium with GTP exchange rate gets higher as a result of activation of DA receptors in the membrane from the mollusc nervous tissues. Influence of the catalytic subunit of the protein kinase A (cPKA) on the [H3]-SKF 38393 and GDP-alpha-P33 is investigated. Obvious influence of the cPKA on [H3]-SKF 38393 binding is not observed, while basal and DA-induced GDP in equilibrium with GTP exchange in membranes of the mollusc nervous tissues is considerably inhibited.

The effect of the thalamic reticular nucleus (RN) stimulation on the spino-bulbo-spinal reflex was studied in chloralose-anesthetized cats. RN stimulation was found to exert an inhibitory influence on this reflex. The same stimulation has also exerted an inhibitory influence on the spinal units activated during the spino-bulbo-spinal reflexes.

An identified monosynaptic peptidergic contact between identified neurons from the brain of snail Helix pomatia L. has been used to study the effect of alpha-latrotoxin. It was found that being applied extracellularly the toxin evoked an increase of the postsynaptic response amplitude. Intracellular injection of the toxin into the soma of the presynaptic neuron led to a decrease of the postsynaptic current amplitude. Current induced by intracellular injection of cAMP into postsynaptic neuron was also inhibited either by extra- or intracellular application of the toxin. According to previous data which demonstrate similarity between the postsynaptic response and the current which was induced by intracellular injection of cAMP into postsynaptic neuron it has been proposed that the toxin evokes both an increase of the transmitter release from the presynaptic neuron and a decrease of the postsynaptic response amplitude.

Electric stimulation of various groups of fibres of cutaneous and muscle nerve of cat has been studied for its effect on action potentials in the gray dorsal column fibres, Registration was performed at the level L2--L3 from ipsi- and contralateral dorsal columns, using needle electrodes. Action potentials of dorsal columns, arisen by stimulation of cutaneous nerves, had a more complex form than those of stimulated muscle nerves. Nonmyelinated fibres of a cutaneous nerve are shown to relate to those of dorsal columns. Excitation of high-threshold A- and C-fibres activates the most fast-conducting fibres of dorsal columns. When a stimulus was applied to all fibres of the cutaneous nerve, the action potentials with conduction velocities of 146-0.24 m/s were recorded in dorsal columns. It was shown that such conduction velocities remained in dorsal columns to level C7. Stimulation of muscle nerves excited only myelinic fibres of dorsal columns, the conduction velocities ranging from 90 to 2.3 m/s. By alternating stimulation of either nerve with a 30-300 ms interval we decreased the action potential amplitude of the nerve that was the second to be stimulated. It is likely be related to convergence of the cutaneous and muscle nerve inputs in the spinal cord on the same neurons. A suggestion is made that faster transfer of high-threshold cutaneous signals in dorsal column are associated with the necessity of rapid information about damaging stimulation.

It is found that vitamins B2 and B6 modified the form of the acetylcholine response in identified Helix pomatia neurons. This effect is mainly conditioned by a delay in desensitization.