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Journal Cover   Neurophysiology
  [SJR: 0.122]   [H-I: 8]   [2 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1573-9007 - ISSN (Online) 0090-2977
   Published by Springer-Verlag Homepage  [2302 journals]
  • Potassium Channels and Signal Transduction Pathways in Neurons
    • Abstract: Potassium (K+) channels constitute the most diverse class of ion channels; these channels are especially important for regulation of the neuronal excitability and provide signaling activity in a variety of ways. These channels are major determinants of the membrane excitability, influencing the resting potential of the membranes, waveforms and frequencies of action potentials, and thresholds of excitation. Voltagegated K+ channels do not exist as independent units merely responding to changes in the transmembrane potential; these are macromolecular complexes able to integrate a great variety of cellular signals that provide fine tuning of channel activities. Compounds that change K+ channel properties are commonly employed as therapeutic agents in a number of pathologies, in particular arrhythmias, cancer, and neurological disorders (psychoses, epilepsy, stroke, and Alzheimer’s disease).
      PubDate: 2015-04-30
       
  • Ethical Responsibilities of the Authors
    • PubDate: 2015-04-28
       
  • Dynamics of the Electrographic Indices in Rats and Hamsters Recovering
           from Artificial and Natural Hypometabolic States
    • Abstract: To induce an artificial hypometabolic state (AHMS) in rats and hamsters (non-hibernating and hibernating rodents, respectively), these animals were subjected to the complex action of hypoxia, hypercapnia, darkness, and low temperature. Natural winter hibernation was also induced in hamsters by housing them in a dark cold chamber. During recovering from the artificial and natural hypometabolic states, we recorded EEG activity (leads were implanted in the frontal and parietal cortices), EMG of the neck muscles, and body temperature. The initial period of self-heating after the AHMS in both species and that in hamsters after hibernation was characterized by low amplitudes of EEG and EMG and clearly pronounced depression of EEG oscillations of all frequency ranges, but with relative predominance of δ oscillations (the latter phenomenon may be partly due to superposition of ECG activity on EEG). In the course of further self-heating of animals, the EEG amplitude increased, and its spectral composition changed. The power of some EEG rhythms reached the maximum, and then the EEG composition was normalized successively beginning from the δ range; then the θ and α ranges and, finally, the βrange were normalized. We observed a certain parallelism between changes in the power of b activity in the composition of EEG and increase in the intensity of muscle activity. Patterns of EEG activity corresponding to one functional state or another (active or passive wakefulness, slow-wave sleep, or paradoxical sleep) were normalized in hamsters approximately two times faster than in rats.
      PubDate: 2015-04-25
       
  • Effects of Neural Crest-Derived Multipotent Stem Cells on Regeneration of
           an Injured Peripheral Nerve in Mice
    • Abstract: We studied the effect of transplantation of neural crest-derived multipotent stem cells (NC-MSCs) obtained from vibrissa germs on regeneration of the injured (transected) sciatic nerve in adult mice (strain FVB). After transplantation of the cells into the injured region, regeneration of the severed nerve was intensified, as compared with that in mice with no implantation. The intensity of vascularization and renewal of the endoneurium also increased. The density of nerve fibers in the distal part of the injured nerve in mice after transplantation of NC-MSCs (10522.8 ± 1044.0 mm–2) was significantly higher than that in mice with nerve injury but without transplantation (8409.5 ± 739.5 mm–2). Possible mechanisms of acceleration of regeneration of the injured peripheral nerve under conditions of transplantation of stem cells are discussed.
      PubDate: 2015-04-24
       
  • Status Epilepticus -Related Hippocampal Injury in the Immature Rat Brain
    • Abstract: Status epilepticus (SE)-related neuronal degeneration and glial activation in different regions of the developing rat hippocampus were investigated in an age- and time-dependent manner. Wistar rat pups of postnatal day (P) 7, 15, and 21 were injected i.p. with lithium+pilocarpine to induce SE or saline to make controls. Rats were sacrificed at 2, 12, 24 h, 3 days and 7 days after SE induction. Neurodegeneration in the hippocampus was assessed by Fluoro-Jade B staining. The expressions of the astrocyte marker (GFAP) and microglia marker (Iba-1) were evaluated by immunohistochemistry. In P7 rats, there was no neuronal damage at any time points in SE. Two hours after SE induction, the number of degenerating neurons in the hippocampus significantly increased in the CA1 region of P15 rats and in both CA1 and CA3 regions of P21 rats. Degenerating neurons in the dentate gyrus appeared at 24 h after SE in P15 and P21 rats. In P7 rats, there was no up-regulation of GFAP- or Iba-1-positive cells in SE. The expression of GFAP was dramatically elevated at 12 h in the CA1 and CA3 regions of P15 rats. The number of GFAP-positive cells did not increase in the dentate gyrus until 24 h after SE induction in P15 rats. In P21 SE rats, the mentioned index increased in the CA1, CA3, and dentate gyrus at 2 h. The number of Iba-1-positive cells increased significantly in the CA1, CA3, and dentate gyrus at 12 h in P15 rats and as early as at 2 h in P21 rats. These findings suggest that SE-related neuronal damage and glial activation in the immature brain are, in general, less intense than in the adult one, and the development of these processes in different structures of the hippocampus demonstrates significant temporal and spatial specificity.
      PubDate: 2015-04-24
       
  • Hysteresis Properties of EMG Activity of the Shoulder Belt and Shoulder
           Muscles at the Development of Isometric Efforts by the Human Arm
    • Abstract: In experiments on rats, we studied the effects of experimental hyperthyroidism (subcutaneous injections of L-thyroxine, 50 μg/kg·day during 7 days) and hypercorticoidism (daily i.p. injections of hydrocortisone, 3 mg/kg·day during 30 days) on parameters of the М responses of the m. tibialis anterior after stimulation of the n. peroneus by single stimuli and their series with the instant frequency increasing linearly from 4 to 74 sec−1. In hypercorticoidism, the latency of single М responses was, on average, 30% longer, while the amplitude was 29% lower than those in the control. Multicomponent М potentials were observed in this group more frequently (in 37.5% of the cases); the duration of these responses demonstrated no significant changes. Hyperthyroidism caused shortening of the latency of the М responses (by 15%) and a decrease in their duration (by 25%). The mean amplitude of the responses exceeded the control by 70%; significant modifications of their shape were not observed. Experimental hyperthyroidism and hypercorticoidism were accompanied by a more expressed decrease, as compared with the control, in the amplitude with increase in the frequency of stimulation of the nerve and decreased stability of generation of the responses. The frequency level at which the inverse dependence between the М response amplitude and stimulation frequency began to be clearly pronounced decreased in animals with the modified hormonal status. Probable reasons for peculiarities of the frequency dependence of the parameters of the М responses in hyperthyroidism and hypercorticoidism are discussed.
      PubDate: 2015-04-24
       
  • Opioidergic Regulation of P2X3 Receptor-Mediated Currents in DRG Neurons
    • Abstract: As is traditionally believed, the analgesic effects of opioids are due to their action on the CNS mechanisms. At present, however, proofs are been accumulated that activation of opioid receptors at the periphery can also result in a strong analgesic effect (especially in the case of inflammatory processes). In neurons of the dorsal root ganglia (DRG) of rats, we examined the effects of activation of opioid receptors on purinergic (P2X3) receptor-mediated ion currents and tried to identify possible intracellular signal pathways between the respective receptors. P2X3-mediated ion currents in DRG neurons were evoked by applications of αβ-Me-ATP. These currents were strongly (on average, by 74%) and reversibly inhibited after application of an endogenous opioid peptide, leu-enkephalin (L-Enk, 100 nM). A selective competitive antagonist of μ opioid receptors, CTOP, completely abolished the effect of L-Enk. We believe that a pathway mediated by phospholipase C (PLC) is involved in intracellular signaling between opioid and P2X3 receptors, and our experiments confirmed this hypothesis. A synthetic activator of PLC suppressed P2X3-mediated currents; an inhibitor of synthesis of phosphatidylinositol 4,5-bisphosphate (PIP2), wortmannin, accelerated and augmented the inhibitory effect of L-Enk on P2X3-mediated currents. Therefore, the inhibitory effect of L-Enk on the latter receptors is based on activation on PLC and hydrolysis of PIP2.
      PubDate: 2015-04-24
       
  • Effects of the Extract of Calophyllum inophyllum on Behavioral Indices in
           Rodents
    • Abstract: We examined modifications of behavioral indices evoked in rodents by introduction of an alcohol extract from leafs of Calophyllum inophyllum (С.i.) under conditions of four neurobehavioral tests. Intraperitoneal injections of 50, 100, or 200 mg/kg of the concentrated extract were used; the effects observed were compared with the action of 1 mg/kg diazepam. In the hole-board test, injections of the C.i. extract significantly suppressed in a dose-dependent manner the manifestations of research behavior (decreased the number of head dips into openings). In the light/dark box test, considerable increases in the time of stay of mice in the dark compartment were observed after extract injections. In the open field test on mice, injections of the C.i. extract resulted in noticeable, while statistically insignificant, decreases in the general intensity of locomotion (number of crossed squares). In this test, the number of manifestations of research behavior (rearings) decreased rather considerably; the number of grooming episodes also became smaller, but suppression of this type of behavior was weaker. Testing of rats in the elevated plus-maze showed that the numbers of entries of the animals into open arms of the labyrinth decreased significantly at all doses of the extract, and the duration of stay in these arms was also smaller. Thus, the extract from the C.i. leafs (that containis significant amounts of biologically active compounds) demonstrates rather considerable sedative effects, but these effects are combined with some anxiogenic action. The results obtained show that anxiolytic/anxiogenic effects of a given agent, observed in different behavioral tests (that are considered specific from this aspect), are not fully identical and should be compared with reservations.
      PubDate: 2015-04-24
       
  • Suppression of GABAergic Synaptic Transmission by Azidin: Probable
           Mechanism of a Seizure-Inducing Side Effect
    • Abstract: Azidin (Berenil, Intervet) is a protisticide drug based on diminazene aceturate. It is widely used in veterinary medicine for the treatment and prophylactics of piroplasmosis, babesioses, and teileriosis. Azidin is not used in clinical practice because of the probability of serious side effects, in particular initiation of seizure activity. We examined the effect of Azidin on evoked GABAergic postsynaptic currents (PSTs) in cultured hippocampal neurons using a patch clamp technique. As was found, Azidin in a concentration equivalent to 40 μM diminazene aceturate provides a more than twofold drop in the amplitude of evoked GABAergic PSTs; the effect develops in 3 to 4 min after application. The diminazene concentration in blood serum after its injection into animals can reach 45 μM; this is why the seizure side effect of Azidin can probably be explained mostly by suppression of GABAergic transmission. A combination of Azidin with positive modulators of GABA receptors can be considered an approach allowing one to minimize its side effect.
      PubDate: 2015-04-24
       
  • Frequency Dependence of Parameters of the М Response of the Rat M.
           Tibialis in the Norm and in Experimental Hyperthyroidism and
           Hypercorticoidism
    • Abstract: In experiments on rats, we studied the effects of experimental hyperthyroidism (subcutaneous injections of L-thyroxine, 50 μg/kg·day during 7 days) and hypercorticoidism (daily i.p. injections of hydrocortisone, 3 mg/kg·day during 30 days) on parameters of the М responses of the m. tibialis anterior after stimulation of the n. peroneus by single stimuli and their series with the instant frequency increasing linearly from 4 to 74 sec−1. In hypercorticoidism, the latency of single М responses was, on average, 30% longer, while the amplitude was 29% lower than those in the control. Multicomponent М potentials were observed in this group more frequently (in 37.5% of the cases); the duration of these responses demonstrated no significant changes. Hyperthyroidism caused shortening of the latency of the М responses (by 15%) and a decrease in their duration (by 25%). The mean amplitude of the responses exceeded the control by 70%; significant modifications of their shape were not observed. Experimental hyperthyroidism and hypercorticoidism were accompanied by a more expressed decrease, as compared with the control, in the amplitude with increase in the frequency of stimulation of the nerve and decreased stability of generation of the responses. The frequency level at which the inverse dependence between the М response amplitude and stimulation frequency began to be clearly pronounced decreased in animals with the modified hormonal status. Probable reasons for peculiarities of the frequency dependence of the parameters of the М responses in hyperthyroidism and hypercorticoidism are discussed.
      PubDate: 2015-04-24
       
  • Effect of Activation of the GLT-1 Transporter by a Beta-Lactam Antibiotic
           on Serotonin-Induced Scratching Behavior in Mice
    • Abstract: Glutamate is believed to be the predominant excitatory neurotransmitter in the networks responsible for itch-related behavior. Beta-lactam antibiotics were shown to exert neuroprotective effects by increasing expression of the glutamate transporter GLT-1. We observed whether repeated administration of the beta-lactam antibiotic ceftriaxone suppresses serotonin-induced itch-related behavior (similarly to the effect of this agent on pain transmission) in mice. Chronic, but not acute, ceftriaxone introductions reduced the number of serotonin-induced scratches; dihydrokainic acid, a selective GLT-1 transporter inhibitor, partly but significantly abolished this effect of ceftriaxone. Our findings suggest that GLT-1 activation by beta-lactam antibiotics looks promising for the treatment of chronic itch.
      PubDate: 2015-04-24
       
  • Effects of Bisphenol A and Learning on the Distribution of GABA Aα1
           Receptors in the Rat Hippocampus and Prefrontal Cortex
    • Abstract: Bisphenol-A (BPA) is a widely distributed chemical having mixed estrogen agonist/antagonist properties. We investigated the effects of introduction of BPA and passive avoidance learning on the distribution of GABAAα1 receptors in the rat prefrontal cortex and hippocampus. BPA (5 and 50 mg/kg·day) was introduced by oral intake for 15 days; learning and memory were tested in a shuttlebox. The distributions of GABAAα1 receptors were investigated by an immunohistochemical procedure. The BPA treatment significantly decreased the density of GABAAα1 receptors in the prefrontal cortex and hippocampus. The distribution of these receptors was significantly denser in BPA-exposed rats subjected to learning than that in rats without learning. Thus, BPA treatment leads to down-regulation of GABAAα1 receptors in the prefrontal cortex and hippocampus. Learning a passive avoidance reaction provides up-regulation of such receptors in these brain structures.
      PubDate: 2015-04-24
       
  • Effects of Aging and Experimentally Induced Modifications of Signal
           Pathways on Insulin-Induced Shifts of Glucose Metabolism in the Rat
           Neocortex
    • Abstract: We studied insulin-induced intensification of glucose absorption and glycogen formation in the neocortex of young and old rats. In young animals, the corresponding shifts were clearly expressed; in old rats, insulin exerted nearly no stimulatory action on the processes of glucose metabolism in neocortical tissues. It was hypothesized that this is due to the age-related enhancement of the level of ceramides resulting in changes of the lipid spectrum of the cell membranes and also due to suppression of key components of signal pathways of insulin in the brain (such as Akt/protein kinase В, ARF, protein kinase С, and phospholipase D). These events disturb the signal cascade of the hormone and process of formation of the physiological response. An increase in the amount of ceramides in neocortical tissues of young animals after the action of exogenous С2 ceramide or palmitic acid (precursor of sphingolipids) was accompanied by suppression of the intensification of glucose absorption and insulin-stimulated formation of glycogen. Taking into account a significant increase in the amount of ceramides in the neocortex of old animals (this was shown in our earlier study), we believe that age-related accumulation of ceramide is an important reason for the development of insulin resistance of glucose metabolism in the CNS of old organisms.
      PubDate: 2015-04-24
       
  • Linear and Nonlinear EEG Synchronization in Alzheimer’s Disease
    • Abstract: As is known, Alzheimer’s disease (AD) is associated with cognitive deficits due to significant neuronal loss. Reduced connectivity might be manifested as changes in the synchronization of electrical activity of collaborating parts of the brain. We used wavelet coherence to estimate linear/nonlinear synchronization between EEG samples recorded from different leads. Mutual information was applied to the complex wavelet coefficients in wavelet scales to estimate nonlinear synchronization. Synchronization rates for a group of 110 patients with moderate AD (MMSE score 10 to 19) and a group of 110 healthy control subjects were compared. The most significant decrease in mutual information in AD patients was observed on the third scale in the fronto-temporal area and for wavelet coherence within the same areas as for mutual information; these areas are preferentially affected by atrophy in AD. The new method used utilizes mutual information in wavelet scales and demonstrates larger discriminatory values in AD compared to wavelet coherence.
      PubDate: 2015-04-24
       
  • Dynamic Properties of Purkinje Cells Having Different Electrophysiological
           Parameters: a Model Study
    • Abstract: Simple spikes and complex spikes are two distinguishing features in neurons of the cerebellar cortex; the motor learning and memory processes are dependent on these firing patterns. In our research, the detailed firing behaviors of Purkinje cells were investigated using a computer compartmental neuronal model. By means of application of numerical stimuli, the abundant dynamical properties involved in the multifarious firing patterns (such as the Max-Min potentials of each spike and period-adding/perioddoubling bifurcations) appeared. Neuronal interspike interval (ISI) diagrams, frequency diagrams, and current-voltage diagrams for different ions were plotted. Finally, Poincaré mapping was used as a theoretical method to markedly distinguish timing of the above firing patterns. Our simulation results indicated that firing of Purkinje cells varies dynamically depending on different electrophysiological parameters of these neurons, and the respective properties may play significant roles in the formation of the mentioned characteristics of dynamical firings in the coding strategy for information processing and learning.
      PubDate: 2015-04-24
       
  • Erratum to: Wavelet Decomposition-Based Analysis of Mismatch Negativity
           Elicited by a Multi-Feature Paradigm
    • PubDate: 2014-12-01
       
  • Erratum to: Peculiarities of Microhemocirculation in the Rat Brain after
           Different Modes of Cold Acclimation
    • PubDate: 2014-12-01
       
  • Disorders of Peripheral Innervation and Regulation of Autonomic Functions
           Evoked by Professional Influence of the Vibration/Noise Factor
    • Abstract: We examined changes in the characteristics of innervation of the upper limb and peculiarities of control of the cardiovascular system in 53 male workers (riveters and fitters in an aircraft plant) who were for a long time subjected to the influence of local vibration and noise in the course of their professional activity. As was found, the mean intragroup threshold of vibration sensitivity of a finger of the working hand in these subjects significantly (P < 0.001) exceeded both normative values and corresponding values in the control group. The respective negative shifts were intensified with increase in the professional experience duration. The mean velocity of transmission of an excitation volley along motor fibers of the n. medianus and n. ulnaris of the working limb in the main group was lower by about 9% (P < 0.05) as compared with the respective index in the control group. Transmission via sensory fibers innervating the corresponding regions of the palm was slowed down by more than 20% (P < 0.05). The residual latency at generation of M responses of the palm muscles in the main group was, on average, 6% longer than in the control (P < 0.05). The mean latency of the evoked cutaneous sympathetic potential at stimulation of the finger of the contralateral palm and recording from the palm and dorsum of the hand also significantly (P< 0.05) exceeded the analogous control value. Results of five standard clinical cardiovascular tests (change in the systolic arterial pressure in the orthostatic test, change in the diastolic pressure at realization of an isometric effort by the palm muscles, calculation of the 30/15 ratio of cardiointervals in the orthostatic test and of the coefficients of duration of these intervals in the Valsalva and deep breathing tests) showed that pathological and boundary values of these indices were found in the main group in 60.3, 32.0, 26.0, 36.0, and 34.0% of the examined persons, while analogous cases in the control group were exceptional. Thus, the long-lasting influence of the intense professional activity-related vibration/noise factor results in the formation of demyelinating polyneuropathy in the upper limb nerves with the involvement of motor fiber terminals and sympathetic postganglionic fibers in the pathological process. Changes in the indices of the cardiovascular tests in subjects of the main group demonstrate that these persons frequently suffer from disorders of the peripheral and, probably, central mechanisms of autonomic control of the cardiovascular system. This results in the development of a syndrome of progressive autonomic insufficiency (with prevalence of insufficiency of the sympathetic mechanisms).
      PubDate: 2014-12-01
       
  • Reorganization of the Forelimb Motor Cortical Zones Under Conditions of
           Chronic Epileptiform Activity
    • Abstract: In rats, we examined the organization of cortical zones within which microstimulation (MES) evoked contractions of separate groups of the forelimb muscles. Examination was performed under conditions of pictrotoxin-induced kindling and within the postkindling period. In kindling rats, the areas of cortical zones responsible for forelimb movements was significantly (more than two times) greater than those in intact animals (P < 0.05). Microstimulation-evoked effects in postkindling were rather similar to those observed under kindling conditions. When longer (1-sec-long) stimuli were used for MES within both kindling and postkindling periods, the duration of motor responses was significantly (P < 0.05) greater than in the control. The enhancement of the areas of cortical representation of the forelimb muscles under conditions of kindling-induced epileptiform activity probably reflects systemic modifications in the motor cortex neuronal systems.
      PubDate: 2014-12-01
       
  • Effect of a Blocker of Nicotine Acetylcholine Receptors on Excitatory
           Postsynaptic Currents in Ganglion Cells of the Rat Retina
    • Abstract: We examined the involvement of nicotine acetylcholine receptors (nAChRs) in the generation of background synaptic activity in rat retinal ganglion cells (RGCs). Experiments were carried out in vitro on RGCs of the isolated retina of 21-day-old rats using the patch-clamp technique in the whole cell configuration (voltage-clamp mode). The neurons did not undergo enzymatic processing in order to provide more adequate preservation of the properties of cells of the native retina. In 15 examined cells, the resting membrane potential (RMP) was –62 ± 2 mV, on average, the input resistance of the membrane was 573 ± 68 MΩ, and the membrane capacitance was 34 ± 5 pF. The effects of blocking of nAChRs were estimated using bеnzohexonium (BH) in a 450 μM concentration. Background excitatory postsynaptic currents (EPSCs) in RGCs appeared, under the conditions of our experiments, with the mean frequency of 3.1 ± 0.8 sec–1 (n = 10). Application of BH resulted in suppression of the currents in six cells. Significant selectivity of the effects of these blockers was observed; it affected mostly high-amplitude EPSCs (40–100 pA). The effect of BH was mostly reversible. Our results show that activation of nAChRs modulate electrical activity in RGCs; probably, these receptors mediate certain types of synaptic transmission. The general RGC population is rather heterogeneous from the aspect of the presence/absence of nAChRs and distribution of separate subtypes of the latter.
      PubDate: 2014-12-01
       
 
 
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