Neirofiziologiia = Neurophysiology最新文献

Development of postsynaptic potentiation (PSP) and desensitization (DS) caused by "non-quantal" acetylcholine after acetylcholinesterase inhibition was studied by means of ouabain, an agent known to modulate (initially increase and then decrease) the level of non-quantal secretion of ACh. Ouabain had no effect on the MEPC parameters when AChE was active. After AChE inhibition ouabain initially increased the decay time constant of MEPC (tau), i.e. caused postsynaptic potentiation (PSP). This effect of ouabain grew with time between inhibition of AChE and application of ouabain. The PSP stage was followed by shortening of MEPCs decay, due to the development of desensitization (DS), and that process was more pronounced than in control. Applied before AChE inhibition, ouabain had no effect on tau. Thus neither PSP nor DS developed under those conditions. Exogenous ACh (20 nmol/l) applied simultaneously with inhibitor of AChE partially prevented the shortening of MEPCs decay, but decreased the amplitude of MEPC. Applied after MEPCs shortening, exogenous ACh (50 nmol/l) tended to return the initial value of tau. It is concluded that nonquantal ACh produces PSP and DS on the postsynaptic membrane after inhibition of ACh and that the DS persists after cessation of nonquantal secretion for a long time.

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.

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.

GABA-immunoreactive (GABA-I) elements (neuronal somata and neuropile) are detected in turtle Emys orbicularis and lizard Ophysaurus spodus in all structures of ventral and dorsal parts of amygdaloid complex (AC) considered as phylogenetic more ancient and younger, respectively by means of the immunohistochemical method. Their maximal quantity in the ventral section of AC is found in the lateral region, lesser--in the ventral, central and medial regions. Besides in lizards a specialized laminar distribution of GABA-I elements in n. sphaericus is observed. GABA-I neurons are also detected in structures of dorsal part in turtles and lizards against the background of the immunopositive neuropile of a moderate density. It is supposed that GABA-ergic innervation of AC is liable to considerable variations in connection with taxonomic, ecological and other factors.

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 role of non-quantal secretion (NS) of acetylcholine (ACh) in shortening of miniature end-plate currents (MEPC) after initial prolongation of MEPC due to acetylcholinesterase (AChE) inhibition was studied in the mouse diaphragm muscle under the voltage clamp conditions. Elevation of NS level by removal of magnesium ions from solution accelerated the shortening effect. After elimination of NS due to an increase of magnesium concentration up to 3 mmol/l the shortening of MEPC was absent. It was suggested that after AChE inhibition the magnesium ions in physiological range of concentrations can modulate the desensitization development on postsynaptic membranes by NS level regulation.

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.

The character of evoked activity of motoneurons, interneurons and Renshaw cells of white rats in low lumbar segments of the spinal cord was studied 5 days after cutting of sciatic nerves. A trustworthy rise of the amplitude of the excited postsynaptic potential (EPSP) of motoneurons on the side of nerve cutting was found. No reliable change of the membrane potential and threshold of the action potential emergence in these motoneurones was observed. Character of evoked activity of the Renshaw cells and interneurons did not differ essentially from the same of animals with the intact nerve. Possible mechanisms taking part in rising of the EPSP amplitude after cutting of the nerve are discussed.