Neirofiziologiia = Neurophysiology最新文献

The role of the celiac plexus in maintaining temperature homeostasis in rats during cold stress was studied histochemically, ultrastructurally, and electrophysiologically. Inhibition on efferent impulses in preganglionic (splanchnic) nerves and facilitation in postganglionic (superior mesenteric) nerves during a short-term cold exposure leading to slight hypothermia were found. In cold-exposed animals after the celiac plexus decentralization, the neurons showed an increase in the fluorescence intensity and activity of energy metabolism enzymes, hyperplasia of fine structures responsible for protein synthesis and energy supply of cells. It is suggested that during cold stress when efferent impulse flow in preganglionic nerves markedly decreases, the celiac plexus becomes a regulatory centre for autonomic functions involved in the maintenance of temperature homeostasis.

The carrying ability of a spinal disc disturbed under axis load is found to be due to the displacement of a vertebra lying above it. The constant stretching of the extensively innervated soft tissues of the spine brings about a steady irritation process within the limits of the segmental part of the spinal cord and dysfunction of short profound muscles of the back.

It is shown in experiments on spinalized cats under electrical stimulation of the pelvic nerve branch innervating the rectum as well as of the fibular nerve that 12 of 30 studied neurons to which the effect of these sources was converged were activated both by A- and by C-fibers. Reactions on stimulation of the fibular nerve were, apparently, mediated by the fibers with the conduction velocity not less than 2.2 m/sec. It is detected in experiments on spinalized rats that tension of the lower sections of the large intestine may evoke activation of neurons of the IV-V layers and inhibition of cells from the deeper layers. The inhibition evoked by the visceral stimulation in seven cases from 18 was provided by the effect directly on the postsynaptic membrane of these cells, in 11 cases it was localized in presynaptic (relative to them) structures. Naloxone, strychnine and atropine did not eliminate this inhibition which testifies against possible participation of opioids, glycines and acetylcholine in its creation. phaclofen, a blocker of the GABAB-receptors was also uneffective while bicuculline suppressed this inhibition in three cases from 12 which testifies to a probability of its participation in creation of GABAA-receptors.

Skin receptors have been studied in the aspect of diverse phenomenology of their participation in organization of motor activity: from the protective flexor reflex to fine correcting effects from the skin which covers the muscle and the tendon. Analysis of the character of exteroceptive effects on reflector responses, cyclic motions and arbitrary activity has revealed a distinct determination of the effect, its dependence on localization and intensity of the exteroceptive stimulus, a moment of its application (state of motor centres) and so on. It is shown that the proprioceptive correction of the motion which underlies the ring control of the motion is inevitably added by exteroceptive effects incorporated into the same system due to their convergence to the same neuronal mechanisms. Basic moments of neuronal organization and basic mechanisms of sensory (exteroceptive) correction of motor activity are considered. Proceeding from the results of the author's investigations, the role of the premotor zone (the ventral horn, L6,7) interneurons which are not connected initially with afferents in the processes of sensomotor interaction in polysynaptic ways to the motoneuron is determined. It is supposed that these neurons integrate already selected information and form a discrete premise to output systems.

Neuronal responses (areas 3, 4, 5) were registered in awake cats after electric stimulation of the contralateralis limb. External stimuli, food and defensive motivation inhibit short-latency neuronal reactions which were registered in control. When in the experiment there was electric stimulation of another limb instead of an external stimuli the neuronal reaction did not change. If subthreshold electric stimulation (SES) was given with a perceptible stimulation of such modality the spike neuronal responses appeared in either cases. This SES may be used as a conditional signal during defensive conditioning. It is established that the neuronal pattern under somatic stimulation is not constant. Its character is connected with fluctuation of cat's exteroceptive attention under external stimuli and internal motivational condition.

The tonic increased influence of the superior colliculus (SC) on the formation of visual responses of the sensorimotor cortex (SMC) was shown on the alert rabbits. It was shown that SC influence was realized through tectothalamocortical (nucleus lateralis posterior) canal relation. It was established that SMC of the alert rabbits in its turn exerts the inhibitory phasic influence on SC function. The obtained data are discussed in the light of participation of the colliculo-cortical and cortico-collicular interactions in the organization of the visual-motor coordination necessary for realization of the visual controlled behaviour.

Single intravenous administration of ethanol (1 g/kg) to experimental cats influences 95% of investigated neurons of the lateral vestibular nucleus. In most (56.5%) neurons possessing primarily high-frequency background activity of the uninterrupted arrhythmic type ethanol administration has caused a decrease in the impulsation frequency by 84-93%; 14.5% neurons of the burst-group activity demonstrate a primary distinct increase of the average frequency of discharges, prolongation of bursts and the numbers of impulses in them changed 20-30 min after ethanol administration by sharp inhibition of the background activity up to its complete ceasing. A distinct exciting effect has arisen due to the ethanol effect during the whole period of observation in 23.6% of neurons mostly with primary low frequency of the background activity. The rehabilitation of the activity up to the primary level as a rule did not appear even 90 min later. Repeated administration of ethanol in the same dose has induced a cumulative effect.

The "concentration clamp" technique has been modified to realize fast and short-term application of a transmitter to whole neuron followed by its fast washout. Prolonged glutamate application evoked activation of the desensitized current. The application time was shortened to intervals when the washout corresponded to unfinished desensitization of the current. Shortening of the glutamate application term to some milliseconds resulted in arising of fast currents which maximal amplitude appreciably exceeded that of currents evoked by prolonged glutamate application. The role of both components under real synaptic conditions is discussed.

Local cooling (14-16 degrees C) and warming (40-42 degrees C) of different crus areas or healthy volunteers have been studied for their effect on pain sensitivity. The latter was estimated by means of the tibialis anterior flexor reflex (FR) and EMC-recording. It was established that changes in FR parameters depended not on the thermostimulus modality, but on its position. The FR was enhanced when the warm or cold stimulus was applied over the ipsilateral tested flexor muscle, and it was mainly inhibited when the thermostimulus was over the extensor or contralateral flexor. An assumption is made that the loss of the temperature modality is caused by convergence of temperature and pain information to the spinal interneurons of the "bimodal type". These neurons change their impulse activity under the effect of both temperature modalities. Different reactions of FR on thermostimulation of different areas of the crus are explained by the locomotor generation control of afferent information.

Rearrangements of the activity parameters of scratching and locomotor generators conditioned by electric stimulation of the inferior olive, nucleus reticularis lateralis as well as of the fastigial nucleus and nucleus interpositus of the cerebellum were investigated on decerebrate immobilized animals. Scratching and locomotor generators were characterized by the ability to effectively rearrange the time structure of their activity in response to certain changes in phase and amplitude characteristics of signals arriving both by the mossy and climbing inputs of the cerebellum. The flexor half-centre of the locomotor generator and aiming half-centre of the scratching generator increased both the period and intensity of their activity under influence of signals arriving to the cerebellum from the inferior olive and nucleus reticularis lateralis at the first half of the working phase of these half-centres. Stimulation of the inferior olive and nucleus reticularis lateralis during the second half of the flexor and aiming phases evoked somewhat different changes in correlation of activity for half-centres of the locomotor and scratching generators. A slight shortening of the activity period of the aiming half-centre during scratching and a decrease of the activity period of the extensor half-centre during locomotion were observed. Stimulation of the structures mentioned above during the working phase of half-centres controlling limb extensor movements evoked shortening of the extensor half-centres activity period during locomotion and exerted no effect on the scratching jerk half-centre activity period during scratching. The scratching generator, unlike the locomotor generator is characterized by a significant degree of resemblance of the rearrangement of generator efferent activity parameters evoked by electric stimulation of the cerebellum nuclei and its afferent inputs. Possible mechanisms of forming the correcting influences on scratching and locomotor generators from the cerebellum during changes in phase and amplitude characteristics of its input signals are discussed.