Neirofiziologiia = Neurophysiology最新文献

Firing of motor units of human soleus, triceps brachii and rectus femoris muscles was studied. Standard deviations of interspike intervals against mean intervals were plotted during voluntary muscle contraction and tonic vibration reflex. There was no significant difference between the results obtained under these conditions.

Thermosensitive points of the man's body skin have been examined in 98 volunteers 20-46 years old living in Alma-Ata in psychophysiological research using temperature and mechanical stimulation. According to thresholds of appearance and quality of sensation two groups of cold-sensitive points and 4 groups of heat-sensitive ones were identified. Receptors of each group located in skin in zones of the greatest concentration. Temperature ranges and the number of sensitive points were compared, which revealed different significance of the skin plots in temperature perception.

The characteristic property of skin cold receptors is the presence of static and dynamic activity with their maximum at any skin temperature. Parallel with the common properties there are some differences in the temperature range of receptors' functioning, frequency of static and dynamic activity, concentration of sensitive receptors on the skin. Mechanisms of these differences are unknown. It is found that the character of skin cold receptors functioning can be changed in individual life of the organism. Some parameters of static and dynamic activity as well as concentration of cold receptors functioning change both with adaptation of the organism to cold and with a rise of the noradrenaline concentration in blood. The reason of adaptive modifications of skin thermoreceptors may be an increase of their sensitivity to noradrenaline observed with adaptation to cold. It can be supposed that the modulating influence of biological active substances is very important in forming activity and sensitivity of skin thermoreceptors.

Impulse activity of cold fibres (n. infraorbitalis) has been studied in acute experiments on anesthetized rabbits, with an uninterrupted fall of the skin temperature from 39 degrees to 7 degrees C with the rate of 0.8 +/- 0.05 degrees/min. Analysis of interspike intervals (ISI) in a discharge of receptors has shown that histograms of ISI changed several times in the studied range of temperatures, which reflects a change of the discharge pattern. Each cold receptor possesses an individual mode of the response, which permits dwelling on perception of different characteristics of the temperature stimulus by a sum of thermoreceptors.

The mode of dopamine action (DA) was investigated both on identified neurons (growth hormone producing cells--GHC) and on the membrane fraction of the CNS tissue homogenate. Adenylate cyclase activity (ACA) in the Lymnaea membrane depended on the GTP, stimulated and inhibited by different well known mediators, dopamine action being one of them. DA produced a stimulatory and inhibitory action on ACA. Direction of the DA action depended on the GTP concentration: at lower concentration of the GTP DA was a stimulator of ACA, at higher--an inhibitor. It is shown that inhibitory influence of DA on ACA was prevented by treatment of the membrane of the catalytic subunit of the protein kinase A (cPKA). It is particularly noticeable that inhibitory influence of cPKA-dependent phosphorylation reduced the inhibitory action of ALF4-, a G-protein activator. Effect of DA application on the GHC induced appearance of inward and outward currents through the neuronal membrane.

Adrenaline, dopamine and 5-hydroxytryptamine enhanced fast desensitizing responses of frog spinal motoneurons evoked by L-glutamic acid. Monoamines also enhanced late components of dorsal root EPSP's of motoneurons. These effects of monoamines were prevented by ketamine. Slow in desensitizing responses evoked by L-glutamic acid and EPSP's of motoneurons evoked by stimulation of the reticular formation were not influenced by monoamines.

Application of serotonin (ST, 1.10(-4) M to periaqueductal grey neurons influenced background activity (BA) only in the third group of cells. In 45.5% of them ST evoked depression of BA. Through application of ST remarkable potentiation of BA inhibition evoked by locus coeruleus (LC), substantia nigra (SN) stimulation was found, but inhibitory affects of nucleus raphe magnus (NRM) were less intensive. After intraperitoneal injection of p-chlorophenylalanine the efficiency of NRM stimulation became lower, but influences of LC and SN on BA increased. The mechanisms of serotoninergic effects on BA of periaqueductal grey neurons are discussed.

The review presents information on morphology, afferent and efferent connections of the ventrolateral medulla, mediator characteristics of neurons within the rostral and caudal parts of the ventrolateral division of the medulla, functional organization of the structures involved in the cardiovascular control.

Chemical nature of carbohydrate components in identified neurons of mollusc Helix pomatia influencing acetylcholine responses was investigated using different lectins (Con A, RCA, WGA and LPA). Differences between Con A-evoked changes in acetylcholine-induced chloride and sodium-potassium currents as well as differences in the time and temperature dependences of these changes showed various mechanisms of action of carbohydrate component with mannose residues on the function of acetylcholine receptors. The analysis of the time and temperature dependences of depressing effects of WGA and RCA on acetylcholine-induced currents permits supposing endocytosis of lectin-receptor complexes with N-acetyl-D-glucosamine residues.

A decrease in the amplitude of miniature and evoked end-plate potentials (MEPPs and EPPs) as well as changes in EPP facilitation and depression during frequency stimulation were observed in psychosine-treated m. cutaneous-pectoris of the frog. Electron-microscopic investigation demonstrated severe changes in synaptic Schwann cells embracing motor terminals and disturbances in the inner mesaxon structure of the myelinated parts of motor terminals.