Neirofiziologiia = Neurophysiology最新文献

Sodium succinate has been studied for its influence on the efficiency of glutamate transmission in the Schaffer collateral synapses and duration of its potentiation state caused by high-frequency stimulation in surviving hippocampal slices. It is shown that administration of sodium succinate (50 mg/kg i. p.) to rats 30 min prior to decapitation stabilizes glutamate transmission in field CA1 of the rat hippocampal slices and increases duration of its potentiation state.

Impulse activity of single afferent fibres of the spinal cord dorsal roots of cats was investigated under local mechanical, heat and cold influence on receptive fields of their skin. These influences did not change the frequency of impulsation, but changed redistribution of interimpulse intervals. It is supposed that formation of polyfunctional properties of single afferent fibres is realized due to their polychannel information.

The paper is concerned with the study of localization, firing properties, methods of activation and projection into the neuronal structures of the medulla oblongata as well as the reflex action of two types of mechanoreceptors of the lungs: slow- and rapid-adapting stretch receptors. Data on the first relay neurons monosynaptically connected with slow-adapting pulmonary stretch receptor afferents are presented.

Intracellular responses of neurons of the suprasylvian gyrus to the intracortical stimulation (ICS) before and after superficial application of strychnine were investigated in experiments on immobilized and unanaesthetized cats. The normal cortex neurons reacted to ICS by monosynaptic EPSPs followed by IPSPs. Strychnine application triggered the epileptiform activity and appearance in neurons of paroxysmal depolarization shifts of the membrane potential (MP) which were replaced by hyperpolarization potentials. An increase and summation of the latter elicited the MP enlargement and either reduction or suppression of background spike activity. Intracellular injections of EGTA blocking the membrane calcium-dependent potassium conductivity (gK(Ca)) have eliminated the hyperpolarization potentials. Development of epileptiform activity was accompanied by depression of IPSPs and increase of the monosynaptic EPSPs. The contribution of gK(Ca) and of postsynaptic inhibition to the epileptogenesis is discussed.

Microcirculation disorders may cause functional deviation in gray matter cells of the spinal cord. One of the setting moments of the disorders is the subluxation of a vertebra as a result of the disturbance in carrying ability of the spinal disc in case of spinal osteochondrosis. In this position the soft tissues of the spinal motional well innervated segment are stretched, which induces irritation in the segmental part of the spinal cord including vegetative nervous structures. Subluxation of a vertebra causes changes in the structures and in the microcirculation vessels which grow simultaneously and this permits supposing their interrelation.

The 45Ca2+ absorption by the different tissues under PTH influence was studied by the radioisotope method as dependent on the incubation time. In all cases it was found that the tissue faculty of 45Ca2+ accumulation increases especially in the early period of the incubation. This effect results from a more intense activity of the membrane channels.

Field potentials (FP) were recorded from radial and pyramidal layers of the mice hippocampus after conditioning and testing stimulations of the Schaffer collaterals. The effect of a preliminary conditioning stimulus on the tested responses (the "priming" effect) was studied for different testing intensities and interstimulus intervals of 50 to 5000 ms. Two series of experiments were conducted. In the first series the influence of the conditioning stimulus delivered with the interval of 200 ms on the testing stimuli of various intensities was studied. The duration of the testing FP in the radial layer was measured. The plot of the FP duration against the stimulus strength revealed three regions. For the first region (at small stimulus intensities) the FP duration was maximal and independent on the stimulus intensities. The second region began at the point where FP duration reduced presumably due to the feed-forward inhibition. The conditioning stimulus caused a widening (recovery) of the FP due to suppression of the inhibition. In the third region the stimulus intensity was sufficient to excite pyramidal cells and therefore to activate the feed-back inhibition. The time course of the FP was contaminated by the population spike and FP duration became inadequate for the evaluation of the "priming" effect. The second set of the experiments was aimed to study possible changes in the feed-back inhibition. With this end in view the influence of the conditioning (priming) procedure on the paired-pulse depression was studied. The main effect of the conditioning was a suppression of the paired-pulse depression, i.e. a suppression of the feed-back inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

In isolated snail neurones the level of cyclic AMP was increased either by intracellular injection of cAMP or by extracellular application of dibutyryl-cAMP and the change of high-threshold calcium current (ICa) decay was investigated. In 20 from 38 neurones it was obtained that both fast and slow phases of ICa decay were accelerated 2-2.5 times as affected by cAMP. The effect did not depend on the test-pulse potential and was displayed on the IBa. In the double-pulse experiments it was shown that cAMP enhanced the influence of depolarized prepulses (Vc) on the ICa tested (It). Analysis of the It-Vc curve showed that cAMP enhanced both Ca(2+)-dependent and voltage-dependent inactivation of ICa. The experiments where the intervals between Vc and Vt varied have shown that cAMP slowed down the rate of Ca(2+)-channels recovery from inactivation. The results suggest that cAMP increases the affinity of the Ca(2+)-channel inactivating substrate for Ca(2+)-ions.

Cutaneous C-fibre polymodal mechano-heat (CMH) sensory units of narcotized cats have been studied for their responses to the close-arterial injection of potassium, acetylcholine and methacholine to the saphenous artery in subnoxious and noxious concentrations. Subnoxious chemical stimulation has induced low-frequency excitation of CMH units. The parameters of CMH units firing during subnoxious and noxious chemical stimulation may be used for estimation of effects of local anesthetics. To achieve local anesthesia it is sufficient to inhibit only high frequency responses in CMH units without a complete block of these sensors. With that end in view the use-dependent blockers of nerve excitation are suggested. The use-dependent inhibition of CMH units was found during mechanical stimulation under the action of lidocaine or n-propylajmaline. The mathematical model of C-fibre has demonstrated the key role of slow changes of membrane ionic permeabilities in determining the firing rate elicited by chemical stimulation.

It was shown in experiments on anesthetized cats that motor cortex (MC) stimulated by single current pulse caused formation of the lateral geniculate nucleus (LGN) response. It was established that changes in formation of LGN response evoked by contralateral superior colliculus (SC) stimulation were observed by condition of the precedence of LGN response evoked by stimulation of the MC. The expressiveness level of that decrease depended on intervals between conditioning cortical and testing tectal stimuli. At the same time the stimulation of the MC by single current pulse caused no changes in formation of the visual evoked potential of LGN. However, a significant decrease of the visual response of that part of the SC which stimulation caused formation of the LGN response was observed under the same conditions. The obtained data permit supposing that MC checks realization of the tectal influences on the LGN function on the tectal level. It is assumed that realization of the effect of the saccadic suppression of the LGN function in which accomplishment, as it was supposed earlier, the SC took part, was controlled by the MC phasic influence.