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Biomedical subjects

V A Korshunov

Publications and source records attributed to V A Korshunov.

At least 19 recordsLinked to original sources
PubMed2006

[Plasminogen activators and matrix metalloproteinases during arterial remodeling].

To evaluate the role and interaction of plasminogen activators and matrix metalloproteinases (MMPs) in arterial remodeling in vivo we compared effects of recombinant urokinase- (uPA) and tissue-type (tPA) plasminogen activators on vessel morphology, cell proliferation, inflammatory reaction and MMPs expression in arterial wall after experimental balloon angioplasty. We observed that the periadventitial application of uPA to the injured artery in pluronic gel stimulated neointima formation and inward arterial remodeling as well as cell proliferation and inflammatory leukocytes recruitment. In contrast, tPA attenuated neointima growth, contributed to outward arterial remodeling and did not affect significantly leukocytes recruitment in injured arterial wall. Perivascular uPA increased the content and activity of MMPs, while tPA did not induce such changes. In mouse model of vascular remodeling based on partial ligation of the carotid the content of uPA correlated with neointima growth, tPA content correlated with outward arterial remodeling. Our experiments suggest that plasminogen activators represent specific functional target for attenuating unfavorable inward arterial remodeling.

Angioplasty↗
PubMed2004

Effect of cholinergic and adrenergic receptor blockade on arrhythmogenic activity of endothelin-1 during inhibition of nitric oxide synthesis in awake mice.

We studied the effects of blockade of nicotinic receptors in sympathetic and parasympathetic ganglia (hexamethonium), muscarinic receptors (atropine), and beta1-adrenoceptors (atenolol) on arrhythmogenic activity of endothelin-1 during inhibition of nitric oxide synthesis with Nomega-nitro-L-arginine in NMRI mice. Atropine reduced, while hexamethonium completely abolished the arrhythmogenic effect of endothelin-1 during nitric oxide synthase inhibition. Atenolol potentiated arrhythmogenic activity of Nomega-nitro-L-arginine, but endothelin-1 had no effect on the incidence of arrhythmias under these conditions.

Adrenergic Antagonists↗
PubMed2004

Stimulation of the lateral hypothalamus provokes the initiation of robust long-term potentiation of the thalamo-cortical input to the barrel field of the adult, freely moving rat.

Long-term potentiation in the thalamo-cortical input to the somatosensory cortex barrel field has been reported to be inducible in vitro only during a narrow critical period of the first postnatal week. Here we explored whether this is due to inability of adult synapses to express LTP or lack of appropriate conditions for LTP induction in slice preparations. We recorded thalamo-cortical field potentials (FPs) from the barrel field of chronically prepared adult rats. In the first series, several parameters of conditioning tetanization of thalamus (T) have been tried. Statistically significant LTP of 135-150% relative to the baseline was observed only in rare cases (3/18) so that the mean changes were not statistically significant. In the second series, five trains of 100 Hz stimulation of T were paired with a "reinforcing" stimulation of the lateral hypothalamus (LH). In most cases (9/13), thalamo-cortical FPs were potentiated. The mean post-tetanic amplitude was 238 +/- 42% (+/- SEM) relative to the baseline (n = 13). The potentiation persisted for >1 h and typically even further increased when tested 24-48 h later. LTP magnitude strongly correlated with the initial paired-pulse ratio (PPR, coefficient of correlation r = 0.98) so that the LTP magnitude was larger (333 +/- 107, n = 6) in cases with PPR > 1.3. The mean PPR tended to decrease after LTP (from 2.05 to 1.65). Altogether the results suggest that LTP is inducible in the thalamo-cortical input to the barrel field of normal adult rats. The dependence of the LTP magnitude upon the initial PPR suggests that inputs with low initial release probability undergo larger LTP. Together with the tendency to a decrease in the PPR this suggests an involvement of presynaptic mechanisms in the maintenance of neocortical LTP.

Animals↗
PubMed2003

Arrhythmogenic effects of endothelin-1 under conditions of NO-synthase blockade with L-NAME in NMRI mice.

Arrythmogenic effects of endothelin-1 were studied in NMRI mice under conditions of NO-synthase blockade with N omega-nitro-L-arginine methyl ester. Intravenous injection of endothelin-1 increased heart rate variability in awake mice. NO-synthase blockade potentiated the arrythmogenic effects of endothelin-1. In narcotized animals the arrythmogenic effect of endothelin-1 was not observed and was considerably weakened under conditions of NO-synthase blockade. Arrhythmia was paralleled by atrioventricular block and lengthening of the ST segment.

Animals↗
PubMed2000

Hemodynamic effects of tetrindol in alert normotensive mice and rats after blockade of nitric oxide synthesis.

Single intravenous injection of antidepressant tetrindol (1 and 10 mg/kg), a reversible monoamine oxidase A inhibitor, dose-dependently decreased heart rate and mean arterial pressure (in a concentration of 10 mg/kg) in alert NMRI mice and Sprague-Dawley rats. Nitric oxide synthase blockade with L-NAME attenuated tetrindol-induced bradycardia in rats and completely abolished this effect in mice.

Animals↗
PubMed2000

[Quantitative characteristics of the systemic anaphylaxis model in Sprague-Dawley rats].

Anaphylactic response intensity was quantitatively estimated by means of measuring mean arterial pressure (MAP) and heart rate (HR). Damage to intestinal mucosa was studied by means of morphometry. These indices grew in a dose-dependent way along with the amount of administered egg ovalbumin (OVA). The MAP and HR measurements seem to be useful in a quantitative elucidation of allergic sensitivity in laboratory animals.

Anaphylaxis↗
PubMed2000

[Genetic aspects of arterial hypertension: the role of Y chromosome and mitochondrial DNA].

A study on hybrids from reciprocal crossing of the SHR-SP and the WKY has shown that Y-chromosome and mitochondrial DNA the affect development of the spontaneous hypertension. The Y-chromosome takes part in disorders of baroreceptive sensitivity in phenylnephrine assay associated with hypertension. Although our findings suggest that structural remodelling of peripheral vascular resistance and an increase in noradrenaline-dependent vasocostriction is genetically determined in hypertensive rats, we could not corroborate the role of the Y-chromosome and mitochondrial DNA in the process. A difference was shown between male and female SHR-SP in the level of arterial pressure and in development of the vascular structure changes.

Animals↗
PubMed1999

Restoration of decaying long-term potentiation in the hippocampal formation by stimulation of neuromodulatory nuclei in freely moving rats.

Induction of long-term potentiation within the hippocampal formation can be modulated by afferent influences from a number of subcortical structures known to be involved in hippocampal-dependent learning and memory. This study performed on freely moving rats investigated the effects of stimulation of the noradrenergic locus coeruleus nucleus and the serotonergic dorsal raphe nucleus on spontaneously decaying posttetanic long-term potentiation in the dentate gyrus and the hippocampal CA1 area, respectively. High-frequency electrical stimulation of the locus coeruleus or the dorsal raphe elicited a well-expressed behavioural reaction of exploratory or defensive type, respectively, but did not significantly alter transmission at perforant path-dentate gyrus or Schaffer collateral-CA synapses, when delivered either before tetanic stimulation of the perforant path or the Schaffer collaterals or long (hours and days) after previously induced long-term potentiation had completely decayed. However, when locus coeruleus or dorsal raphe stimulation was delivered with the same parameters during a limited time (minutes and hours) after marked or even complete decay of tetanus-induced long-term potentiation at perforant path-dentate gyrus or Schaffer collateral-CA1 synapses, the potentiation was partially or entirely restored but never increased beyond the initial level of potentiation. In CA1, stimulation of ipsilateral and contralateral Schaffer collaterals demonstrated that the restoration of previously existing long-term potentiation by dorsal raphe stimulation was input-specific, occurring, like tetanus-induced potentiation, only in the pathway which had previously been tetanized. These findings suggest that the noradrenergic locus coeruleus and the serotonergic dorsal raphe can influence not only induction, but also spontaneous decay of long-term potentiation in the hippocampal formation. Since hippocampal long-term potentiation is thought to play a role in certain kinds of learning and memory, and association of tetanic stimulation with activation of ascending neuromodulatory systems is required for full expression of long-term potentiation, the restoration of hippocampal long-term potentiation by activation of a neuromodulatory system alone may serve as a mechanism of associative reminder which may underlie facilitation of memory retrieval after a period of forgetting, as has been observed in trained rats under similar conditions.

Animals↗
PubMed1996

Place- and behavior-independent sensory triggered discharges in rat hippocampal CA1 complex spike cells.

To test for access of spatial cues to the hippocampus of unrestrained animals, single unit recordings of CA1 complex spike cells were made in thirsty rats as they made alternating visits between the center and corners of an enclosed 60 x 60 cm square arena. At intervals, all lights were turned off in the arena and it was rotated. Although no neuronal discharge activity was found that encoded the rotation angle, 11 of 97 neurons were selectively activated after lights were turned off or on. This activity began at delays of up to several seconds and persisted for tens of seconds. These discharges had no location selectivity or behavioral correlates and continued even as the rat performed several behaviors in different parts of the arena. This confirms similar results in restrained rabbits while showing for the first time that this neuronal activity can be independent of place and behavior. In addition this shows that sensory stimuli can trigger hippocampal discharges even when the rat is not required to make any behavioral responses to them.

Animals↗
PubMed1995

Place-independent behavioural correlates of hippocampal neurones in rats.

The broad diversity of discharge correlates of hippocampal neurones has provoked controversy. For example, purported behavioural correlates could, instead, be location selectivity (of 'place cells') that is secondarily modulated by sensory stimulation or ongoing movements. In rats trained to perform identical behaviours in four corners of a symmetrical arena, we found hippocampal pyramidal cells discharged selectively as the rats performed task-related behaviours regardless of spatial location. Since the ensemble of these hippocampal neurones comprehensively represented all stages of the task, we propose that each cell represents an element of the temporal organization of the animal's behaviour, complementing the place cell representations of elements of the structure of the environment.

Action Potentials↗
PubMed1995

Inertial, substratal and landmark cue control of hippocampal CA1 place cell activity.

Hippocampal 'place cells' discharge when a rat occupies a location that is fixed in relation to environmental landmarks. A principal goal of this study was to determine whether hippocampal place cell activity could be influenced by inertial cues. Water-deprived rats were trained in a square-walled open field in a dark room. The behavioral task required alternating visits to water reservoirs in the centre and in the four corners of the arena. The rat and arena were rotated in total darkness through +/-90, 180 or 270 degrees C. The next water reward was then presented in the corner at the same position relative to the outside room as before the rotation. A cue card was later illuminated in this corner as a visual cue for the extra-arena (room) reference frame. Fifteen out of 97 recorded hippocampal CA1 complex spike cells had spatially selective discharges in non-central parts of the arena. After arena rotations, the firing fields of three units shifted between corners of the arena to maintain a fixed orientation relative to the room. This indicates that the hippocampus updated its representation of the position and heading direction of the rat using vestibular-derived inputs concerning rotation angle. Other spatially selective discharges were guided to landmark cues (cue card or position of the reward: two units) or arena-locked 'substratal' cues (eight units). In six cells, place cell activity suddenly ceased or appeared following rotations. These results provide evidence for contributions of inertial as well as substratal and landmark information to hippocampal spatial representations.

Animals↗
PubMed1995

Miniature microdrive for extracellular recording of neuronal activity in freely moving animals.

The new design of a removable miniature microdrive for extracellular recordings of single-unit activity in freely moving animals with high-impedance electrodes is presented. The construction permits very simple installation and removal of the microelectrodes, rapid fixation of the microdrive on the animals skull and rapid removal after recording. The microdrive provides vertical positioning of the electrode without rotations and lateral shifts, stable recordings of single units for several hours and the possibility to change the penetration track 20-30 times in the same animal. The 3.2-mm diameter of the microdrive cylinder permits the installation of several units simultaneously. The weight of the microdrive with the base is 115 mg. The microdrive permits penetrations to any desired depth.

Animals↗
PubMed1989

[An experimental approach to research on the integrative properties of a single brain neuron].

The difficulties in investigation of the single neuron integrative properties in mammalian brain are connected with the absence of a mean of determination of neuronal set contribution in their activity. In given paper an experimental approach to the decision of this task is proposed. It consists in neuron activity investigation in the model learning training situation under condition of partial functional isolation from nervous cells by means of decrease in extracellular calcium concentration level using ethylene glycol tetraacetate. As indicator of such isolation was a partial or total reduction of responses in investigated neurons to electric microstimulation of neighbouring (200-240 mkm) parts of neocortex. The results of analysis of neuron responses in sensomotor cortex in the rat's brain in the process of acetylcholine repetitive local application give possibility to propose that some neurons don't exhibit plasticity according to the indicator in the dynamics of impulse discharge rate in responses to transmitter.

Acetylcholine↗