Neirofiziologiia = Neurophysiology最新文献

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.

Neuronal impulse activity in the sensorimotor cortex after Substantia Innominata (SI) stimulation has been studied in cats during conditioned placing with food reinforcement. SI stimulation was delivered 1 or 3 seconds before the conditioned sound stimuli. The results of the investigation show that SI stimulation does not change sensorimotor cortex impulse activity but at the same time it inhibits the background activity. Reactions of 32% (after 1 s) and 33% (after 3 s) of the somatosensory cortex neurones were increased to conditioned stimuli and conditioned movement after preliminary SI stimulation. The appearance of impulse responses in some neurones which showed no initial reactions to conditioned stimuli was caused by SI stimulation. Preliminary SI stimulation may cause not only excitatory but also inhibitory effect on somatosensory cortical neurones. In case of 1 s interval between SI stimulation and conditioned stimuli presentation there were only 6% of cells with such inhibition, but in case of 3 s interval there were 33% of such reactions. SI stimulation shortened the latencies of the conditioned movement 2-3 times. Modulatory influence of acetylcholine from SI neurones to neocortical activity is discussed.

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)

Distribution of primuline, fast blue, fluoro-gold and nuclear yellow-labelled monoamine-containing cells in periventricular gray and dorsolateral tegmentum (including locus coeruleus) was studied in the rat after injection of these fluorochromes into the frontal cortex, hypothalamus and spinal cord. Combination of monoamine fluorescence method and retrograde cell-labelling was used. Two big groups of serotonin-positive cells projecting into the upper thoracic spinal segments were found in dorsomedial zone of the dorsal raphe. Part of these units also had divergent axon projections to the frontal cortex. Such cellular arrangement allows a supposition that analgetic effects of dorsal raphe stimulation can be partially based on the direct participation of this structure in the descending control at the spinal level. Neurones, sources of cortical projections are intermingled with the cells projecting to the hypothalamus but some topical differentiation can be distinguished. Neurotransmitter and neuroregulatory roles of separate cortical and hypothalamic projections of serotonin-containing neurons of the dorsal raphe cells is discussed.

Mechanisms of the exogenic acetylcholine (ACh) effect on ionic currents of nerve endings (NE) were investigated by extracellular recording of NE at the cutaneous pectoris muscle of frog. It was found that ACh in concentrations 0.1-0.6 mmol/l increased the third phase of the nerve ending response, while in concentrations 0.7-2.0 mmol/l-decreased it. Tubocurarine and atropine did not alter the ACh effect. It has been also revealed that growth of the third phase of NE response, induced by ACh, occurs in the presence of calcium channel blockers and disappears under the influence of 4-aminopyridine and tetraethylammonium. In calcium-free solution or when the calcium current is blocked the suppressive effect of ACh disappears. The mechanisms of exogenic and endogenic ACh effects on the potential-sensitive and calcium-activated potassium NE currents are discussed.

Serotonin (5-HT) added to washing solution has been studied for its effect on plastic properties of electrically excitable membranes of the parietal ganglion and identified PPa2 neurons in the isolated nerve system of snails. It is shown that neurons habituated to intracellular stimulation are able to restore action potential generation in the presence of 5-HT. Contrary, neurons possessing endogenous rhythmic activity (PPa2) generate train activity on the background of appearance of the membrane potential slow waves under the influence of 5-HT. A comparative analysis of 5-HT and chemicals with the known effect on activity of Ca and Ca-dependent K-channels (quinine, CoCl2, CdCl2) has demonstrated diversity of mechanisms underlying the 5-HT-ergic regulation of plasticity of the neuronal electrically excitable membrane. This difference stems from the processes of activation and blockade of Ca-dependent channels.

Studies of spontaneous firing (SF) in the midbrain periaqueductal gray (PAG) neurons before and after stimulation of nucleus raphe magnus, locus coeruleus and substantia nigra were performed on the rat anesthetized with Hexenal (200 mg/kg). Three types of neurons different in SF structure were found. Stimulation of indicated structures increased SF rate in 11-14.5% and decreased 31-47% of the studied neurons of the third group. Simultaneous stimulation of two structures did not induce a remarkable increase of SF rate. If one of two simultaneously stimulated structures suppressed SF the ultimate effect was, as a rule, depression of SF. Greatest suppression of SF was observed if stimulation of nucleus raphe magnus was induced. Role of PAG in organization of the brain stem component of antinociceptive mechanism is discussed.