Neirofiziologiia = Neurophysiology最新文献

Penicillin (PCN) has been studied for its effect on the membrane potential (MP) and synaptic activity of lamprey spinal cord motoneurons using intracellular recording in the in vitro spinal cord-notochord preparation. In one group of motoneurons with relative low MP (58.7 +/- 5.2 mV, n = 28) PCN induced depolarization, enhancement and prolongation (up to 80-220%) of the initial amplitude of excitatory postsynaptic potentials (EPSPs) evoked by the stimulation of dorsal roots spinal tracts. If the MPs (in the other group of motoneurons) were high (70.0 +/- 5.7 mV, n = 20) depolarization was not observed and the potentiation of EPSPs did not exceed 25-70% of the initial value. These effects of PCN can be eliminated by a preliminary addition of excitatory or inhibitory amino acid antagonists in the superfusion solution. The obtained results allow suggesting the presence of two different acceptor sites for PCN in membranes of lamprey spinal cord motoneurons.

Space likeness of crystal cells of GABA, glycine, muscimol and taurine has been estimated by special calculation. The relation between the likeness degree of crystal cells and their biological effect on amino acid receptors is marked.

It has been found that neuroblastoma cells retract their neurites under the influence of ether in dose 1 ml in 15 ml of the cultural medium. Application of ether for two hours increases the ratio of the number of cells to the number of neurites from 9.94 +/- 2.12 in the initial state to 19.66 +/- 1.93 (P less than 0.002). An essential alteration of the cell shape and a decrease of their volume are observed as well. The reaction is typical of cells at different stages of morphological differentiation. The data obtained can be helpful for investigation of pharmacological preparations which prevent destruction of neurons under narcosis.

Extension and flexion cortically-evoked movements (CEMs) were studied in the framework of the experimental approach developed in the previous paper [5]. Movements in the elbow joint of an unanesthetized cat were evoked by intracortical microstimulation (ICMS) applied to the motor cortex, then they were tested using a torque disturbance method. Similarity of flexion and extension CEMs allowed producing their combined quantitative analysis and comparing the obtained characteristics with those defined for the movements which were evoked by direct stimulation of the biceps and triceps muscles in an anesthetized animal. Resulting stiffness and uncertainty index (UI) served as the main characteristics of the movement in the presence of torque disturbances. Depending on the relationship between the directions of the preceding movement and the initial phase of the disturbed one, CEMs were divided into two types: coinciding (1) and opposing (2) CEMs. When the preceding movement was evoked by switching on of ICMS, both types of the disturbed movements could be considered as realizations of the phasic myotatic reflexes: unloading (1) and stretch (2). Disturbed movements of type 1 were characterized by the narrow range of mean values of UI: 0.43-0.91 (1.2 Hz wave of torque disturbance) and 0.24-0.73 (3.2 Hz). Transition to type 2 enlarged sharply the spread in the means, they could be both positive and negative, variances of UI in separate realizations significantly increased as well. It is supposed that intensity of central processes controlling the disturbed movements is mainly connected with changes in their direction but not with the movement per se.

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.

The focused ultrasound has been used for the comparative study of skin sensitivity to pain in 51 healthy men and 64 patients with neurasthenia, natural model of the chronic psycho-emotional stress. The patients showed a distinct tendency to a decrease of the pain threshold, lowered adaptation to the repeated threshold stimulus, sensitization. With the presence of the above-mentioned factors the pain syndrome occurred relatively more often. Taking into account the fact that the focused ultrasound of rather high intensity affects, first of all, C-afferents which are not only cutaneous but visceral nociceptors as well, an assumption is made that changes in pain sensitivity in the neurasthenic patients are not limited by skin but develop also in the inner medium forming the pain syndrome.

Activity of myelinated fibres in the n. saphenus was investigated by the crosscorrelation method in the cat's skin stimulated by heat and burn. The decrease of the total nerve activity under the heat action is proved to be related mostly to a change in A beta-fibres. It is shown that pain caused by heating of the skin over 42 degrees C activated A delta-fibres. The results obtained permit solving the problem of the heat information code from the view-point of the flow "pattern" theory.

Responses of neurons in the medulla and cervical segments to simultaneous repetitive (50 pps) stimulation of two locomotor points (LPs) by currents in the range of 1 to 2 thresholds of locomotion were studied. In most cases a neuron responded to stimulation of only one LP. Stimulation of the second LP enhanced usually the firing index of that response, if it was low, diminished it, if it was high and did not influence it, if it was about 0.2. Part of neurons increased the background activity during stimulation of one of LPs though spikes were not locked to stimuli. A sign of influence of the second LP onto that elevation depended on its value. Data about the convergence of inputs from the ipsi- and contralateral midbrain and bulbar LPs on single neurons were obtained too. Possible mechanisms of summation of subthreshold excitation of two LPs during initiation of the locomotion are discussed.

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.