PubMed Health⌕ Search

Biomedical subjects

M V Samoĭlova

Publications and source records attributed to M V Samoĭlova.

11 recordsLinked to original sources
PubMed2001

[Structure of glutamate receptor ion channels and mechanisms of their blockade by organic cations].

Structural determinants of blocking the glutamate receptors of AMPA and NMDA subtypes, were studied. Close location of hydrophobic and ammonium groups is necessary for affective blocking of the NMDA receptor channels, whereas blockers of the AMPA receptor channels have a distance of about 10 angstroms between these two groups. Models of the channels meeting these topographic data have been devised using a molecular mechanics approach. The accomplished studies revealed molecular basis of channel blockade of the NMDA and AMPA receptors. This may allow designing predictable new blocking compounds with a desired selectivity.

Adamantane↗
PubMed2000

[Structural characteristics of ionotropic glutamate receptors revealed by channel blockade].

The topography of the channel binding site in glutamate receptors (AMPA and NMDA types of rat brain neurons, receptors of molluscan neurons and insect muscle), and in two subtypes of nicotinic cholinoreceptors (in frog muscle and cat sympathetic ganglion), has been investigated by comparison of the blocking effects of mono- and dicationic derivatives of adamantane and phenylcyclohexyl. The channels studied can be divided into two groups. The first one includes AMPA receptor and glutamate receptors of mollusc and insect, and is characterised by the absence of activity of monocationic drugs and the strong dependence of dicationic once on the internitrogen distance in the drug molecule. The second group includes NMDA receptor and both nicotinic cholinoreceptors. Contrary, here the blocking potency of monocations and dications are practically equal irrespective of molecule length. The data obtained suggest that hydrophobic and nucleophilic components of the binding site are located close to each other in the channels of the NMDA receptor type but are separated by approximately 10 A in the AMPA receptor channel.

Adamantane↗
PubMed1994

[The effect of divalent cations on the kinetics of the activation and blockade of the nicotinic cholinoreceptor ion channel in rat skeletal muscle].

The influence of alkaline earth metal ions calcium and magnesium on the conductance and on the kinetics of activation and atropine-induced blockade of nicotinic cholinoreceptor ion channels in cultured rat skeletal muscle were studied using patch-clamp technique. In physiological concentrations these cations influence both conductance and kinetics of blockade, but have no significant effect on the kinetics parameters of activation. The data suggest that physiological cations modulate the generation of postsynaptic potentials in the normal condition as well as in the presence of blocking drugs.

Acetylcholine↗
PubMed1989

[A single calcium channel with anomalous rectification in mollusk neurons].

The patch clamp technique was used to examine the properties of an inward-rectifying potassium channel in the cell membrane of freshwater mollusc Planorbarius corneus neurons. Inward currents of single channels were observed at potentials more negative than potassium equilibrium potential (EK), when microelectrode contained potassium ions (50 mmol/l) and potassium channel blockers: tetraethylammonium, barium or cesium ions (10-20 mmol/l). The conductance of the single channel was equal to 81 +/- 12 pS at 50 mmol/l potassium ion concentration in the patch electrode. At potentials more positive than EK the conductance sharply decreased to 0 pS. The times of the open state of the closed one of the channel and probability of the open state existing for the ionic channel were estimated with various constant potentials. It was revealed that the channel openings were grouped in bursts. The lifetime of the open state and burst duration decreased with hypopolarization of the patch.

Action Potentials↗
PubMedDate not supplied

Selective block of AMPA/kainate receptors of hippocampal interneurons as a new approach to the investigation of inhibitory system.

Effects of open channel blockers of AMPA/kainate receptors have been examined using whole cell recordings and kainate application in the neurons freshly isolated by vibrodissociation from the rat hippocampal slice preparation. Although the hippocampal neurons differed little in the voltage-current relations and sensitivity to kainate, a prominent difference was found in their susceptibility to the blocking action of adamantane derivatives studied. The pyramidal neurons had low sensitivity to the open channel blockers but the neurons which might be assigned most probably to the group of inhibitory interneurons proved to be highly sensitive. A group of neurons of intermediate sensitivity have also been found. The ability of the same blocking drugs to depress the excitatory inputs in the inhibitory interneurons has been demonstrated in the experiments on the hippocampal slice preparation. Enhancement of the field spike and excitatory postsynaptic potential amplitude was observed in the presence of adamantane derivatives. An additional treatment of the preparation with a GABA receptor antagonist, bicuculline, did not potentiate this effect. In conclusion, the observed difference in the pharmacological properties of inhibitory interneurons may be effectively used for detailed analysis of the brain synaptic transmission.

Adamantane↗
PubMedDate not supplied

[Comparative research on synaptic transmission in the sympathetic ganglia of rabbits and frogs during acetylcholinesterase inhibition].

Organophosphorus inhibitor of acetylcholinesterase (AChE) armin (1 x 10(-6) M) induced a variety of pre- and postsynaptic effects resulting from the AChE inhibition and subsequent accumulation of acetylcholine (ACh) in the synaptic cleft. The intensity of postsynaptic effects (level of neuron depolarization, degree of action potential depression) was shown to be different in the ganglia of frog and rabbit. This could be explained by differences in the total amount of ACh released in response to nerve stimulation as well as at rest. Both muscarinic and nicotinic cholinoreceptors were involved in the process of sustained depolarization of the neurons in the rabbit superior cervical ganglion after AChE inhibition. In frog ganglion neurons the nicotinic receptors did not participate in depolarization evidently due to their fast desensitization. The activation of presynaptic muscarinic receptors resulted in decrease of ACh released by nerve stimulation seems to weaken depolarization and blockade of synaptic transmission in sympathetic ganglia treated by AChE inhibitors.

Acetylcholinesterase↗