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K V Baev

Publications and source records attributed to K V Baev.

At least 37 records · Page 2Linked to original sources
PubMed1989

Peculiarities of receptor-channel complexes for inhibitory mediators in the membranes of lamprey spinal cord neurones.

Effects of inhibitory mediators on the membranes of isolated lamprey spinal cord neurones were investigated by means of whole-cell recording and concentration clamp techniques. Glycine and gamma-aminobutyric acid (GABA) applications evoked desensitizing chloride currents. The concentrations at half-maximum effects were 16 microM for glycine- and 1.5 mM for GABA-activated currents. Ionic responses to applications of both amino acids demonstrated full cross-desensitization. Strychnine and bicuculline suppressed both glycine- and GABA-activated conductances to the same degree. We suggest that in the membranes of lamprey spinal cord neurones glycine and GABA act on the same receptor-channel complexes.

Animals↗
PubMed1988

[Changes in the segmental reactions in the decerebrate cat during scratching and locomotion].

Experiments on decerebrate cats have shown that N1 component potential of dorsal surface and dorsal root potential elicited by electrical stimulation of paw plantar surface tonically decrease during locomotion and scratching. Phase changes occur against a background of tonic changes in the rhythm of limb movements. The dynamics of the observed changes correlates well with that of primary afferent depolarization during these movements. It is concluded that presynaptic inhibition underlies the changes in segmental reactions.

Action Potentials↗
PubMed1988

[Action of l-DOPA and acidic amino acids on isolated neurons of spinal cord in the lamprey].

Ionic currents induced by application of L-3, 4-dihydroxyphenylalanine (L-DOPA) and acidic amino acids: L-glutamate, kainate, N-methyl-D-aspartate (NMDA) were investigated in experiments on isolated spinal cord neurons of the lamprey by means of whole-cell recording and concentration clamp methods. L-DOPA was found to activate glycine, but not excitatory amino acid receptors.

Amino Acids↗
PubMed1988

[Characteristics of the effect of glycine and gamma-aminobutyric acid on the spinal cord neurons in the lamprey].

Responses of isolated spinal cord neurons of lamprey on glycine and gamma-aminobutyric acid (GABA) were investigated by means of intracellular perfusion and concentration clamp techniques. Responses on both amino acids exhibited fast but not full desensitization. Preincubation of neurons in the solution of one mediator led to full disappearance of the response to other mediator. It is suggested that these amino acids act on the same channel-receptor complex.

Animals↗
PubMed1988

[Characteristics of limb movementss, intensity of integral afferent impulse flow from limb receptors and level of polarization of primary afferent endings during locomotion of highly decerebrate cats].

Correlations between parameters of electrical muscle activity, changes of joint angles of the hindlimb, intensity of afferent inflow and dorsal root potential during real locomotion were studied in highly decerebrate cats. Characteristics of the hindlimb movements before and after deafferentation were described. It has been shown that during locomotion the afferent activity consisted of two components: tonic and periodic phase ones. In the latter one three principal waves can be distinguished, each inducing appropriate changes in primary afferent terminals polarization level. These changes in their turn, were summated with those elicited by central generator. Correlation dependences between parameters of the above mentioned processes were investigated. Mechanisms of afferent control of the locomotor generator function are discussed.

Action Potentials↗
PubMed1988

[Changes in the intensity of integral afferent inflow from limb receptors and the level of polarization of primary afferent endings in the decerebrate cat during scratching].

The experiments performed on decerebrated cats have shown that afferent activity during scratching consisted of two components--tonic and periodic phasic ones. The first component was determined by the limb position, the second was closely related to the amplitude and velocity of joint angle changes. Maximum of integral afferent activity in the cycle coincided with the scratching jerk phase. These two components of afferent activity evoked corresponding depolarization changes in primary afferent terminals and these changes added to those elicited by central generator. Statistical correlations between the aforementioned parameters were studied. The afferent control mechanisms of scratching generator are under discussion.

Action Potentials↗
PubMed1987

[L-glutamate-activated membrane conductance of spinal cord nerve cells during the early embryogenesis of the chicken].

Transient and steady-state L-glutamate-activated membrane currents were investigated by means of intracellular perfusion, voltage clamp techniques and concentration clamp in spinal cord neurons of 6-11 day chick embryos. The Hill coefficient was found to equal 1 for transient and 2 for steady-state components. Concentration of L-glutamate evoking half effect decreased during development more than 10 times for the steady-state component whereas it remained constant for the transient component. Existence of two types of glutamate-activated receptors in the membrane of spinal cord neurons at early stages of embryonic development is supposed.

Animals↗
PubMed1987

[Changes in the density of L-glutamate- and glycine-activated currents in the membranes of spinal cord nerve cells in the early stages of chick embryo development].

The changes in densities of L-glutamate- and glycine-activated currents through the membrane of spinal neurons were investigated in 6-11 day chick embryos using enzymatic isolation of cells and voltage clamp technique. General tendency of the current density increase during cell differentiation was found. A considerable decrease of the glycine-activated current density against a background of such an increase was observed on the 9th day of incubation. Reciprocal relation between L-glutamate- and glycine-activated current densities was found for a single neuron. Functional significance of the revealed density changes is discussed in connection with the development of the locomotor function of the spinal cord.

Animals↗
PubMed1987

[Changes in presynaptic processes during tonic subthreshold activation of the spinal center of scratching movements in the cat].

In immobilized intercollicularly decerebrated cats tonic underthreshold activation of the spinal scratching generator (after application of tubocurarine or bicuculline on C1-C2 segments) is accompanied by an increase in primary different terminal depolarization, decrease in N1-component of cord dorsum potential evoked by stimulation of cutaneous afferents, decrease in the amplitude of DRP and early polysynaptic responses of motoneurons evoked by stimulation of cutaneous and muscle afferents; a respective rise and reduction in activity of intermediate nucleus interneurons which are mono- and di (oligo)-synaptically connected with afferent terminals. Spinalization of animal led to reverse changes. Injection of DOPA into spinal animals allowed comparing changes in the state of lumbar segmental apparatus during tonic underthreshold activation of spinal scratching and locomotor generators.

Animals↗
PubMed1987

[Changes in the excitability of motor neurons and synaptic effects on them during formation of the generator of scratching movements in the cat].

It is shown that the state of the segmental apparatus of the lumbal spinal cord of immobilized intercollicularly decerebrated cats during formation of a scratching generator is essentially different from that of a spinal animal. The excitability of "aiming" and "scratching" motoneurons increases, recurrent and reciprocal Ia inhibition of motoneurons becomes stronger and influence of Ib afferents weaker. The flexor reflex afferents exert inhibitory influences on "aiming" motoneurons. After spinalization these influences become excitatory, and the inhibitory influences on "scratching" motoneurons become weaker. The functional role of described changes is discussed.

Animals↗
PubMed1987

[Structural organization and connections of the locomotor strip of the medulla oblongata of the cat].

The bulbar locomotor strip was studied by means of the horse-radish peroxidase technique. HRP microinjections were carried out under functional control of the evoked treadmill locomotion. The experiments have failed to reveal a special cellular column along the locomotor strip and the existence of such a strip as a separate structural formation is questioned. In fact the bulbar locomotor strip may conceal the spinal trigeminal tract and its nucleus. It is postulated that nonspecific afferent activation of the brainstem reticular formation plays a significant role in the locomotion initiation.

Animals↗
PubMed1987

[Readjustment of the efferent activity of the scratching generator in response to stimulation of muscle afferents of the hindlimb of the decerebrate immobilized cat].

Rebuildings of the scratching generator activity caused by phasic electrical stimulation of ipsilateral hindlimb muscle nerves during different hindlimb positions were studied in decerebrated immobilized cats. Strong dependence of these rebuildings on the stimulation phase was observed. The character of the "scratch" cycle duration rebuilding was formed by the scratching generator tendency to bring efferent activity into such correlation with the stimulus that the stimulation moment coincided with the moment of efferent activity phase triggering. Phasic altering of the efferent activity intensity rebuilding was observed against a background of "aiming" and "scratching" activity correlation shift in the direction of strengthening activation of muscles innervated by the stimulated nerve. This rebuilding was intensified when the hindlimb deflects from the aimed position in the direction of corresponding muscles stretching. Physiological sense of "rebuilding absence phases" is discussed. It is postulated that absence of the duration and intensity changes can be achieved simultaneously only with definite correlation between phase and intensity of the afferent impulsation burst.

Animals↗
PubMed1987

[Readjustment of the efferent activity of the scratching generator in response to stimulation of cutaneous afferents of the hindlimb of the decerebrate immobilized cat].

Rebuildings of the scratching generator efferent activity caused by the phasic electrical stimulation of ipsilateral hindlimb skin nerves during different hindlimb positions were studied in decerebrated immobilized cats. Stimulation was followed by short latency inhibition of the efferent activity. Stimulation did not cause correlation shifts in the common "aiming" and "scratching" activity. Changes in the efferent activity cycle duration and intensity depended on the stimulation phase. Inversion of intensity changes occurred with transition from the middle-force to strong stimulation. A functional role of the dependence of the efferent activity rebuilding on the stimulation phase is considered. The scratching generator is supposed to contain a model of the afferent inflow which enters the spinal cord during real scratching.

Animals↗
PubMed1986

[Features of the electrical responses of isolated neurons of the chick embryo spinal cord to L-glutamate application].

Isolated cells from the spinal cord of chick embryo were investigated under conditions of intracellular perfusion and voltage clamp using the method of rapid application of extracellular solutions. Two components were found in the L-glutamate-activated current: a fast-inactivating component and a steady one. The dose-response relationship demonstrated one-to-one interaction between L-glutamate and membrane receptor with Kd values about 0.75 X 10(-5) mol/l for the steady component and 3.2 X 10(-5) mol/l for the fast one.

Animals↗
PubMed1986

[Changes in the excitability of motor neurons and synaptic effects on them during the formation of a locomotor generator in the cat].

It is shown on decorticated (high-decerebrated) and spinal cats and on spinal cats injected with DOPA that the activation of the spinal locomotor generator is accompanied by an increase of the extensor and a decrease of the flexor motoneurons' excitability, an increase of the recurrent and reciprocal Ia inhibition, a decrease of Ib and flexor reflex afferent influences on motoneurons. The possible physiological role of changes in tuning of the spinal segmental apparatus in the generation of the locomotor rhythm is discussed.

Animals↗
PubMed1986

[Presynaptic mechanisms of the change in segmental responses accompanying the formation of the spinal locomotor generator in the cat].

It is shown on unanesthetized immobilized decorticated cats that spinalization of the animal leads to depolarization of the central afferent terminals, decrease of early polysynaptic responses in motoneurons and dorsal root potentials (DRP) evoked by stimulation of the low-threshold cutaneous and muscle afferents, increase of early polysynaptic responses and DRP evoked by stimulation of high-threshold muscle afferents, reduction in the activity of intermediate nucleus interneurons mono- and polysynaptically connected with primary afferents, rise of the activity of interneurons di- and oligosynaptically connected with primary afferents. Injection of DOPA into spinal animals leads to opposite changes. Dependence between changes in the state of segmental neuronal apparatus and the level of spinal locomotor generator activity are discussed on the basis of the data obtained.

Animals↗