Neirofiziologiia = Neurophysiology最新文献

Electrical activity of three different isolated identified bursting neurons in the Helix brain is studied. A new method for isolation of identified neurons is worked out. The data obtained demonstrate that all three neurons are endogenous oscillators: isolated neurons reveal spontaneous changes from inactive condition to regular activity, from regular activity to bursting one and on the contrary. Moreover it is shown that bursting activity in all three isolated neurons can be regulated by the same neurochemical agents: serotonin, enkephalins; combined action of dopamine and enkephalins stimulates bursting activity in these neurons, while dopamine inhibits it. The possible role of these neurochemical mechanisms in generation of rhythm for different rhythmical functions is discussed.

A new approach for the whole-cell recording in slices is suggested as simpler and less expensive one than those known before. Electrophysiological characteristics of excitatory postsynaptic currents are obtained. Two types of glutamate receptors are shown to be involved. The kynurenic acid is proved to exert more prominent effect on the NMDA-receptor mediated current. Biphasic action of adenosine, a wide spread neuromodulator, on synaptic transmission is shown.

In the brain stem of 30-day-old kittens three types of Golgi-stained neurons are distinguished: sparsely branched reticular neurons, densely branched arborescent neurons and multipolar giant neurons (according to the classification by Leontovich). Implication of the new method of computer morphometry permits obtaining formalized characteristics of 23 parameters of the above types of neurons. An analysis of the quantitative characteristics of the studied neurons has revealed statistically significant differences in most parameters. This fact permits advancing a conclusion about morphological identity (stability) of each type of the neurons. Structural differences and similarities in reticular nuclei are discussed with respect to their functional features.

Glycine-activated whole-cell currents of the chick spinal cord neurons have been investigated in a chicken embryo during different periods in culture. Shifts in the concentration dependence curve of mature and immature cells are shown. Mature cells prove to be motoneurons and die 5-7 days later in vitro. immature cells are neuroblasts differentiating in culture. Glycine sensitivity of low-differentiating cells increased more than 10 times by the end of the 14th day in culture. Desensitization kinetics of the glycine-activated currents decelerated with age. A crucial role of spontaneous electric activity was shown for maturation of the agonist-activated conductance.

The comparative analysis of dimensions of horseradish peroxidase labelled vestibulo-spinal neurons and neutral red stained neurons of undifferentiated areas of the vestibular nuclei have been performed in guinea pig. The undifferentiated areas of the vestibular nuclei consisted of small, medium, large and giant cells. A decrease in the relative numbers of small- and medium-diameter neurons and an increase in the relative numbers of large and giant neurons have been observed along the caudo-rostral axis of the vestibular complex. The vestibulo-spinal populations included neurons of medium, large and giant dimensions. The numerical superiority of large and giant neurons have been found. The even distribution of the vestibulo-spinal neurons of different diameters have been revealed along the longitudinal axis of the brainstem.

It is shown that vitamin E (tocopherol) and arachidonic acid are antagonists at the cellular level in regulation of Ca-calmodulin-dependent acetylcholine-induced current in molluscan neurons.

In the chronically isolated slab of the cat auditory cortex when lower layers were additionally undercut and one, two or three cortical layers under the pial surface remained structurally intact, impulse reactions of slab neurons to the intracortical stimulation applied on the other side of this additional undercut were investigated. High effectiveness of axo-dendritic and axo-spinal excitatory contacts formed by nerve elements of intracortical origin in the upper cortical layers was shown. Participation of geniculo-cortical fibres in the spread of excitation in the cortex through synaptic contacts in layer I with dendrites of pyramidal neurons of the lower layers is discussed. The possibility to generate polysynaptic excitatory reactions by neurons shows that in the isolated cortical slab with an undercut of the lower layers the complex interneuronal relations are retained.

The Ca2+ indicator Fura-2 was used to measure changes of cytoplasmic free Ca2+ concentration ([Ca2+]in) in isolated neurons of the snail Helix pomatia occurring through prolonged plasma membrane depolarization. An amplitude of Ca2+ response did not practically depend on value of depolarization in the presence of 5 mmol/l of caffeine unlike normal solution, which permitted suggesting that caffeine activated calcium-dependent Ca2+ release from the intracellular stores, which was a main factor of [Ca2+]in increase during depolarization. The processes of [Ca2+]in relaxation to the rest levels were approximated monoexponentially and occurred 2 times more rapidly in caffeine than in normal solution. An increase of the [Ca2+]in relaxation rate was provided probably, by a rise in the efficiency of the intracellular Ca2+ pumps able to decrease the rest level of [Ca2+]in even lower than that one under normal extracellular solution conditions.

The effect of substance P on the end-plate currents (EPC) and miniature EPC (MEPC) was studied in the "cut" sartorius muscle of the frog using voltage-clamp technique after acetylcholinesterase inhibition. Substance P in the concentration 5.10(-7)-1.10(-6) mol/l had no effect on the amplitude and time course of the single EPC and MEPC, but promoted significant prolongation of EPC decay during repetitive nerve stimulation (10/s), which indicated development of postsynaptic potentiation. Elevation of the substance P concentration to 5.10(-6) mol/l has led to the shortening of single EPS decay and more significant depression of the EPC amplitude in trains. This effect was connected with a decrease of the postsynaptic membrane sensitivity to acetylcholine, i. e. development of desensitization.

Influence of external stimuli and food motivation on neuronal spike responses (area 7) induced by conditional and unconditional stimulation were studied in the awake cats. The beginning of external stimuli and food motivation inhibited neuronal responses after electro-cutaneous stimulation. During external stimulation after the reflex onset conditional neuronal reactions were later by 50-250 ms, but the latencies of conditional movements did not change. Identical changes of neuronal responses were during variation of food motivation. It is supposed that the reason of the studied phenomenon is variation of the exteroceptive attention level of cats induced by changes in experiment conditions.