Showing papers in "Neurophysiology in 1994"
TL;DR: Postural responses to vibrostimulation of muscles of the back surface of the neck were studied in healthy subjects to assume that “neck-evoked” motor events are mediated via central mechanisms that are involved in perception of the head and body position in space.
Abstract: Postural responses to vibrostimulation (50–100 Hz, 0.5 mm, 4–8 sec) of muscles of the back surface of the neck were studied in healthy subjects. In the sitting position, vibrostimulation evoked local displacements (backward head deflection), but global postural responses (forward inclination of the whole body) developed in the standing position. The amplitude of the evoked body inclination was dependent upon the site of the vibrostimuli application along the vertebral column. Asymmetrical application of vibrostimuli to the muscles of the right or left neck side was accompanied by development of a lateral component in the postural response. Changes in the spatial orientation of the head led to the changes in postural response direction: head turning to the right resulted in right-side body deviation during vibration, and vice versa. Illusions of head bend caused by habituation to its static turning were accompanied by precisely the same changes in the direction of body deviation. It is assumed that “neck-evoked” motor events are mediated via central mechanisms that are involved in perception of the head and body position in space.
29 citations
TL;DR: A sensitizing treatment with 5–10% quinine solution causes short-term and long-term changes in the activity of the command neurons for defensive behavior in the snailHelix lucorum.
Abstract: A sensitizing treatment with 5–10% quinine solution causes short-term (lasting 50–70 min) and long-term (lasting several hours) changes in the activity of the command neurons for defensive behavior (LPl1 and PPl1) in the snailHelix lucorum. The short-term effects are characterized by a depolarizing shift in membrane potential, increased excitability, and an initial increase in the content of bound calcium (Ca-c) in the neurons. The long-term effects appear as facilitation of synaptic components of neuronal responses to sensory stimuli without any changes in excitability and in membrane potential, and also as a repeated increase of Ca-c content. Treatment with anisomycin or cycloheximide during sensitization acquirement prevents development of long-term sensitization.
10 citations
TL;DR: Thiamine and TMP, which are normally present in the extracellular medium, may modulate synaptic transmission, as well as the electrical and contractile activity of the smooth muscles in the gastrointestinal tract.
Abstract: Effects of thiamine, thiamine monophosphate (TMP), and thiamine diphosphate (TDP) on excitatory cholinergic and inhibitory noncholinergic nonadrenergic neuromuscular transmissions were studied in the smooth muscles of the gastric fundus and in the circular layer of the distal colon of the guinea pig, respectively. It was found that, when applied in the physiological concentration range, thiamine, TMP, and TDP evoked depolarization and an increase in strain in the smooth muscle strips, as well as an increase in the amplitude of inhibitory synaptic potentials and postinhibitory depolarization. The amplitude of the excitatory synaptic potentials increases in the presence of thiamine and TMP, and decreases in the presence of TDP. The results obtained suggest that thiamine and TMP, which are normally present in the extracellular medium, may modulate synaptic transmission, as well as the electrical and contractile activity of the smooth muscles in the gastrointestinal tract.
9 citations
TL;DR: In the primary visual cortex of an immobilized awake cat, nearly one-third of the neurons studied were found to respond to flashing cruciform light stimuli 1.5–4 times better than to single stimulations with the strips of preferred orientation.
Abstract: In the primary visual cortex of an immobilized awake cat, nearly one-third of the neurons studied (8 out of 22) were found to respond to flashing cruciform light stimuli 1.5–4 times better than to single stimulations with the strips of preferred orientation. It is suggested that such neurons can detect angles and line intersections.
6 citations
TL;DR: It is suggested that the observed features of the synaptic plasticity in command neurons during learning are based on the selective regulation of synaptic inputs by specific protein regulators, whose lifespan does not exceed 1 h to 3 h.
Abstract: The long-term changes in the electrical activity of command neurons related to sensitization and elaboration of associative defensive behavioral habit (food rejection) were studied inHelix snail. The long-term effects consisted of facilitation of synaptic components in neuronal responses to the test stimulations. Variations were found in the dynamics of long-term synaptic facilitation of responses to the applied chemical and tactile stimuli in the course of sensitization, as well as dependence of the degree of long-term facilitation of responses to the test stimulation at the site of its application with respect to the site of the sensitizing stimulation (“site-specific” sensitization). After conditioning, the synaptic response of command neurons to the conditioning stimulation appeared approximately 30 min later than did the long-term sensitization in these cells. The minimum duration of long-term synaptic facilitation of responses to the test stimulation varied from 1 h (for tactile stimulation) to 3 h (for chemical stimulation). The maximum duration of effects exceeded 4 h. It is suggested that the observed features of the synaptic plasticity in command neurons during learning are based on the selective regulation of synaptic inputs by specific protein regulators, whose lifespan does not exceed 1 h to 3 h.
6 citations
TL;DR: It was found that hydrophobicity of the latrotoxin-like protein increases along with the fusogenic activity, and the possible participation of the protein in neurosecretion processes is hypothesized.
Abstract: A latrotoxin-like protein isolated from the bovine brain promoted fusion of negatively charged liposomes consisting of phosphatidylcholine, phosphatidylethanolamine, and cardiolipin in a molar ratio of 2:3:5. The fusogenic effect significantly increased at mild acidic pH 6.0 and under denaturation (4 M urea, 0.1% SDS). Using ANS as the fluorescent probe, it was found that hydrophobicity of the latrotoxin-like protein increases along with the fusogenic activity. We hypothesize the existence in the protein molecule of conformational changes promoting the fusion, and the possible participation of the protein in neurosecretion processes.
6 citations
TL;DR: Results obtained inin vitro conditions have shown that Ca-binding nonhistone proteins of chromatin are components of the cell nucleus whose content may be measured by chlortetracycline fluorescence.
Abstract: Electrophysiological effects have been studied in command neurons of withdrawal behavior inHelix snail. In parallel, correlated changes in the content of bound calcium (Ca-b), as well as changes in DNA condensation, were investigated using a chlortetracycline fluorescent probe and the fluorescent dye bisbenzimide, respectively. Short-term electrophysiological changes (depolarization of the membrane and elevation of its excitability) in sensitized snails have been found to be accompanied by an increase in the Ca-b level in the cell nucleus and by partial DNA decondensation. Long-term effects were characterized by more pronounced synaptic components of the responses — slow EPSPs evoked by sensory stimuli, as well as by further DNA decondensation and considerable elevation of the Ca-b content in the nucleus and cytoplasm. The results obtained inin vitro conditions have shown that Ca-binding nonhistone proteins of chromatin are components of the cell nucleus whose content may be measured by chlortetracycline fluorescence.
5 citations
TL;DR: The ventrolateral nucleus of the thalamus (VL) is considered as a relay motor nucleus that is a nodal point where the pathways from the cerebellum, vestibular nuclei, and main structures of the extrapyramidal system converge.
Abstract: Classifications based on the functional approach [1-4 ] consider the ventrolateral nucleus of the thalamus (VL) as a relay motor nucleus. This nucleus is a nodal point where the pathways from the cerebellum, vestibular nuclei, and main structures of the extrapyramidal system (the striopallidum and the substantia nigra) converge. Information from the VL is further transmitted to the motor, premotor, and accessory motor zones of the brain cortex [5, 6 ]. Functional organization of the VL was studied in numerous experiments, as well as in the course of stereotaxic operations on patients with extrapyramidal motor disorders, when electrophysiological techiques were used for treatment. It must be mentioned that successful curative effects of neurosurgical interventions in some types of extrapyramidal pathology, when a local operative influence on the VL was used, considerably promoted experimental investigation of the VL. At present, the VL is the main target structure that is lesioned for the treatment of many diseases causing hyperkineses. Among them are Parkinson's disease, torsion muscle distony, spastic torticollis, double athetosis (infantile paralysis), hemibaUismus, resting tremor, hepatocerebral dystrophy, Huntington's chorea,
5 citations
TL;DR: The effect of therapeutic-intensity ultrasound on neuromuscular transmission and spontaneous electrical and contractile activity in smooth muscles of the gastrointestinal tract of guinea pig was studied by a modified sucrose-gap technique and the action of ultrasound was found to facilitate the acetylcholinergic neuromUScular transmission.
Abstract: The effect of therapeutic-intensity ultrasound on neuromuscular transmission and spontaneous electrical and contractile activity in smooth muscles of the gastrointestinal tract of guinea pig was studied by a modified sucrose-gap technique. The action of ultrasound was found to facilitate the acetylcholinergic neuromuscular transmission (mainly by increasing the amplitude of excitatory postsynaptic potentials). The higher efficiency of the nonadrenergic neuromuscular transmission was manifested as an increase (nearly twofold) in the total duration, but not in the amplitude, of inhibitory postsynaptic potentials. Modulations of the first and second components of the potentials caused respectively by the action of ATP and of nitric oxide as possible transmitters, were different. Concurrently with enhancing the synaptic transmission efficiency, ultrasound exerted an opposite, inhibitory, effect on generation of spontaneous action potentials and contraction of smooth muscles. All the ultrasound effects were fully reversible. The findings permit assuming a special mechanism of modification of the synaptic transmission in smooth muscles under the action of ultrasound.
5 citations
TL;DR: Analysis of the d-sparteine effect on the dose—response relationship suggests that d-SP at concentrations of 0.5–5.0 µM exerts both voltage-independent and voltage-dependent competitive actions on nicotinic acetylcholine receptors, compatible with a voltage- dependent competitive blocking mechanism.
Abstract: Effects of d-sparteine (d-SP), a ganglionic blocking agent, on membrane currents evoked by iontophoretic applications of acetylcholine to rat superior cervical ganglion neurons, were studied using a whole-cell patch-clamp recording technique. Blocking effects of d-SP were enhanced by membrane hyperpolarization to potentials more negative than −50 mV. Analysis of the d-SP effect on the dose—response relationship suggests that d-SP at concentrations of 0.5–5.0 µM exerts both voltage-independent and voltage-dependent competitive actions on nicotinic acetylcholine receptors. No use-dependence of the d-SP-induced blockade was found using paired ACh applications at interpulse intervals longer than 0.5 sec. Inhibitory constantKi estimated by the Dixon method was equal to 0.62±0.15 and 0.28±0.08 µM at membrane potential levels −30 and −90 mV, respectively. These characteristics of the d-SP blocking effects are compatible with a voltage-dependent competitive blocking mechanism. The possibility remains that an open channel-blocking mechanism with a comparatively fast kinetics contributes to the d-SP-induced blockade, but its contribution is small.
4 citations
TL;DR: In this paper, the presence of guanine di- and triphosphate as well as of their nonhydrolizable analogs amplified the binding of dopamine receptors to membrane DA receptors, especially after EGTA addition.
Abstract: Reception of labeled dopamine [7,83H] DA (hereafter, DA) and of a D1 receptor agonist, [3H] SKF 38393, in membranes from nerve tissues of the fresh-water lunged mollusc,Lymnaea stagnalis, was investigated. The presence of 10−6 to 10−5 M of guanine di- and triphosphate as well as of their nonhydrolizable analogs amplified the binding of agonists to membrane DA receptors, especially after EGTA addition. Replacement of EGTA with EDTA partly suppressed the binding amplification effect. Higher concentrations of guanine nucleotides (10−3 to 10−4 M) inhibited the binding of DA and of its agonists. The GDPβS-dependent stimulation of agonist binding was found not to be induced by subunits of GTP-binding proteins (G proteins), immunologically similar to β1-, β2-, and Goα-subunits of G protein in vertebrates. Membrane phosphorylation by a catalytic subunit of cAMP-dependent protein kinase fully inhibited the stimulating effect of guanine nucleotides on the agonist binding to DA receptors and markedly depressed the DA-dependent GTPase activity.
TL;DR: A comparison of anticonvulsive effects in a series of aliphatic alcohols methanol-ethanol-propanol-butanol showed that all these substances are potent anticonVulsants.
Abstract: Effects of phenazepam and aliphatic alcohols (methanol, ethanol, butanol, and propanol) on associated epileptic complex created in the rat brain cortex by applications of strychnine were studied. Phenazepam considerably suppressed the epileptic foci and their complexes in a dose-dependent manner. A comparison of anticonvulsive effects in a series of aliphatic alcohols methanol-ethanol-propanol-butanol showed that all these substances are potent anticonvulsants. Propanol and butanol reduce epileptic seizures most intensively, but, at the same time, they are most toxic. Application of labelled4C-ethanol showed that anticonvulsive effects strongly correlate with changes in the ethanol concentration in the blood.
TL;DR: The findings support the earlier hypothesis that assigned the studied neurons to spontaneously discharging inhibitory CGS interneurons, which control the activity of efferent CGS neurons.
Abstract: Effects of aspartate (2 · 10−5 M), substance P (10−7–10−8 M), and serotonin (5-hydroxytryptamine, 5-HT; 5 · 10−5 M) on the background activity of neurons in the central gray substance (CGS) were studied on slices of the rat midbrain. Aspartate and substance P (transmitters of nociceptive signals), and 5-HT (modulator of transmission of nociceptive influences) were found either to facilitate or to depress the activity of CGS neurons. The predominant effect of substance P or 5-HT applications to neurons of the dorsal CGS part was facilitation, and to neurons of the ventral CGS part, inhibition. The effects of aspartate application on studied CGS neurons were of varying nature, but inhibitory effects were found to prevail. The findings support our earlier hypothesis that assigned the studied neurons to spontaneously discharging inhibitory CGS interneurons, which control the activity of efferent CGS neurons. The role of tested substances in the regulation of CGS neuronal activity and the antinociceptive CGS effects is discussed.
TL;DR: In the course of neurosurgical interventions in 40 patients with parkinsonism and torsion muscle dystonia, the background activity was recorded from 124 neurons of the ventrolateral nucleus of the thalamus with the aid of microelectrodes during demarcation of boundaries between nuclear structures, and identification of zones within a nucleus.
Abstract: In the course of neurosurgical interventions in 40 patients with parkinsonism and torsion muscle dystonia, the background activity (BA) was recorded from 124 neurons of the ventrolateral nucleus (VL) of the thalamus with the aid of microelectrodes during demarcation of boundaries between nuclear structures, and identification of zones within a nucleus. The following characteristic features of the BA in patients with parkinsonism were found: a relatively large proportion (71%) of cells with a burst pattern of activity; a great diversity of burst duration in the activity (short or prolonged bursts); a large proportion (67%) of cells with cyclic changes in the BA frequency; diverse patterns of cyclic modulation, where periods varied from fractions of a second (0.2–0.8 sec) to seconds (2–10 sec) or to tens of seconds (20–40 sec); cyclic successions of spike bursts with the rhythm typical of the peripheral tremor (3–7/sec) in a substantial proportion (40%) of the units.
TL;DR: With the development of severe behavioral disturbances, amplitude of spontaneous saccadic eye movements gradually decreased, and high total MPTP doses suppressed fast phase of the reflex.
Abstract: In twoMacaca rhesus monkeys that received repeated N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) injections (single dose 0.2 mg/kg, i.m.; cumulative dose 11.2–13.3 mg), changes in characteristics of spontaneous saccadic eye movements and vestibulo-ocular reflex (VOR) were evaluated. With the development of severe behavioral disturbances, amplitude of spontaneous saccadic eye movements gradually decreased. Pronounced changes in duration of saccadic eye movements, frequency of spontaneous saccades, and their pattern were observed. No changes in parameters of VOR slow component were recorded, but high total MPTP doses suppressed fast phase of the reflex.
TL;DR: Signs of reparative processes together with destructive ones have been observed in part of the nigral neurons, and the former may be indicative of the possibility of structural and functional restoration of intracellular organelles.
Abstract: Effects of a specific neurotoxin, N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which selectively affects dopaminergic structures, on the substantia nigra pars compacta, caudate nucleus, ventrolateral thalamic nucleus, hippocampus, and cerebellar cortex have been studied by electron microscopy in cats. Mass damage of the neuronal somata and axon terminals was observed only among the nigrostriatal neurons up to complete destruction in almost half of units. The majority of remaining neurons demonstrated a varying degree of dystrophic changes, mainly of the hydropic type. Submicroscopic characteristics of damaged nigral neurons indicated the disturbance of permeability of neuronal plasma membranes, disorders of the water-salt metabolism, suppression of mitochondrial functions, and disintegration of structural proteins, etc. However, signs of reparative processes together with destructive ones have been observed in part of the nigral neurons. The former may be indicative of the possibility of structural and functional restoration of intracellular organelles. Participation of the elements of the blood-brain barrier in the mechanism of general MPTP toxicity is discussed.
TL;DR: The results indicate that the NMDA-potentiating activity of the above nootropic drugs may be based on both intracellular phosphorylation of NMDA receptor-channel complexes, as mediated by protein kinases, and allosteric enhancement of affinities of these complexes to excitatory amino acids.
Abstract: Nootropic drugs of various chemical structure (pyracetam, dimethylaminoethanol, ethymisol, and ambocarb) possessing antiamnesic activity were found to increase depolarization evoked by L-aspartate and the EPSP late components evoked by dorsal roots stimulation (DR-EPSP). Experiments were performed on motoneurons of the lumbar region of isolated frog spinal cord superfused with Mg2+-free saline. When ionic channels of NMDA-glutamate receptors were blocked with ketamine and Mg2+, the nootropic substances did not affect DR-EPSP and motoneuronal depolarization evoked by L-glutamate. Butamid, a protein kinase A inhibitor, blocked the ethymisol and pyracetam effects, whereas polymixin B, a protein kinase C inhibitor, blocked the ambocarb effect. Trifluoroperazine, a calmodulin inhibitor, blocked the effect of dimethylaminoethanol. Proline inhibited only the pyracetam effect. These results indicate that the NMDA-potentiating activity of the above nootropic drugs may be based on both intracellular phosphorylation of NMDA receptor-channel complexes, as mediated by protein kinases, and allosteric enhancement of affinities of these complexes to excitatory amino acids.
TL;DR: The data indicate that diadenosine polyphosphates enhance the activity of N-type but not of L-type or P-type Ca2+ channels in many central neurons of the rat brain.
Abstract: Modulatory effects of diadenosine tetraphosphate (Ap4A) and diadenosine pentaphosphate (Ap5A) on Ca2+ channels were studied on isolated hippocampal neurons and synaptosomes taken from the rat midbrain. In experiments on synaptosomes obtained from the whole brain, Ap5A applied at a concentration of 100 µM increased the intrasynaptosomal calcium level (measured by means of spectrofluorometry) for 26±1.8 nM, i.e., by 24±2%. Nifedipine failed to block this effect in synaptosomes and in hippocampal neurons. The high voltage-activated Ca2+ currents were identified by recording from freshly isolatedCA3 neurons using a whole-cell patch-clamp technique. Current-voltage relationships were measured in control and after incubation with 5 µM Ap5A. In the majority of tested pyramidal neurons, the latter procedure resulted in a reversible increase in the high voltage-activated currents through Ca2+ channels measured at a holding potential of −100 mV, but not of −40 mV. Potentiation of the currents through Ca2+ channels in hippocampal neurons as well as an increase in intrasynaptosomal [Ca2+] could be irreversibly blocked by 5 µM θ-conotoxin, but not by 200 nM θ-Aga-IVA. These data indicate that diadenosine polyphosphates enhance the activity of N-type but not of L-type or P-type Ca2+ channels in many central neurons of the rat brain.
TL;DR: It is concluded that when duration of force development is not limited, the motor program of such reaction (especially in the Rnd mode) is more “liberal” than in the case of limitations, which contradicts the widespread notions about principles of scaling.
Abstract: The targeted isometric force steps developed by a human wrist after an acoustic signal under conditions of regular repetition and random alternation (the Reg and Rnd modes) of three visually presented target levels (25 N, 35 N, and 50 N) were studied. The main components (MC) and postcorrections could be easily differentiated in the majority of the force trajectories (FT). Analysis of MC parameters has shown that the Rnd mode in comparison with the Reg one is characterized by a noticeable increase in mean amplitude errors of MC with respect to the target level; as a rule, mean errors were positive for the 25 N target level and negative for the 50 N level. An increase in the amplitude variability and a weaker correlation of the force amplitude and the peak value of the first force derivative by time (the maximum rate of the force increase) were also typical of the Rnd mode. It is concluded that when duration of force development is not limited from above, the motor program of such reaction (especially in the Rnd mode) is more “liberal” than in the case of limitations [5, 12]: values of the force increase rate, specified by the central program, determine the force amplitude in a less rigid manner. Program transferring, i.e., the use of the central program of a fast ballistic movement to make a fast isometric force step, is regarded as a possible reason for the above-mentioned discrepancy; the “rigidity” of the program of the fast movement is regarded to be determined by corresponding biomechanical limitations. Correlations of the amplitudes and durations of the FT MC varied a great deal for different tested persons and in different modes, but there was a substantial positive correlation in the majority of cases. This finding contradicts the widespread notions about principles of scaling, when scaling of some parameters and maintenance of other parameters of targeted motor reactions as invariants are postulated. Correspondence of the resulting data to the concept of the generalized motor programs and its modifications is discussed.
TL;DR: Responses of neurons of the lateral (LPO) and medial (MPO) subdivisions of the preoptic region and of the supraoptic nucleus (SO) of the hypothalamus at infusions of a hypotonic or a hypertonic NaCl solution or an isotonic glucose solution into the homolateral internal carotid artery were studied in acute experiments on ketamine-anesthetized cats.
Abstract: Responses of neurons of the lateral (LPO) and medial (MPO) subdivisions of the preoptic region (RPO) and of the supraoptic nucleus (SO) of the hypothalamus at infusions of up to 400 µl of a hypotonic (0.2%) or a hypertonic (0.3%) NaCl solution or an isotonic (5.5%) glucose solution into the homolateral internal carotid artery were studied in acute experiments on ketamine-anesthetized cats. Changes in the firing frequency were exhibited by 69% of the examinedRPO andSO neurons, the response being of four different types: a monophasic increase (1st-type) or a monophasic decrease (2nd-type) in the activity; biphasic responses where an initial frequency rise was followed by inhibition (3rd-type) and vice versa (4th-type). Of all the neuronal responses to all stimulations, 50% (121/245) were of the 1st type; 11% (26/245), of the 2nd type; 5% (14/245), of the 3rd type; and 3% (7/245), of the 4th type. No neurons with 1st-type responses to infusion of the hypotonic NaCl solution were found in the medial sections of theMPO, and of the hypertonic solution, in the lateral sections of theLPO. Neurons with 2nd-type responses to infusion of hypo- and hypertonic NaCl solutions were almost solely detected in theSO, whereas units with such responses to glucose infusions were observed only in theRPO, being fully absent in theSO, where this stimulation gave rise only to 1st-type responses. Neurons with 3rd- and 4th-type responses to hypo- and hyperosmotic stimulations were detected predominantly in theMPO andSO, and to glucose stimulation, in theMPO andLPO.
TL;DR: The findings show that the two pathways controlling the H Reflex function independently, and apparently there exist at least two corresponding groups of interneurons causing a presynaptic inhibition of the H reflex.
Abstract: Effect of an isometric voluntary contraction of the soleus muscle (5–6 sec in duration) on the H reflex was studied in persons aged 25–45 years. A sharp enhancement of the H reflex at a dynamic phase of fast contraction (in the force increase period) and its less pronounced increase at a static phase of contraction were shown. When a paired stimulation of the nerve was used (interstimulus interval, 500 msec), a voluntary contraction of the muscle fully abolished the first stimulus-related suppression of the second H reflex. When the muscle contracted against the background of vibration, the suppressed H reflex recovered up the the level observed in the resting muscle, but did not reach the level characteristic for the contracting muscle. The findings show that the two pathways controlling the H reflex (descending and afferent) function independently, and apparently there exist at least two corresponding groups of interneurons causing a presynaptic inhibition of the H reflex.
TL;DR: It has been suggested that the interrelation between the parameters of SPD and τMEPC is an important factor regulating the amplitude and duration of the postsynaptic signal.
Abstract: The effect of correlation between the kinetics of acetylcholine (ACh) quanta release and the kinetics of the postsynaptic membrane channel activity on end-plate currents (EPCs) was studied in model experiments. The presynaptic process was described by a transmitter secretion probability distribution (SPD), and the postsynaptic process by characteristicsof miniature EPC (MEPC) with standard amplitude and variable decay duration (τMEPC). The SPD was represented by a curve with an S-like rise and exponential decay. The main portion of the data was analyzed after being adjusted to 20°C. The effect of the EPC amplitude loss (the difference between the EPC amplitudes in cases of synchronous and non-synchronous release of the ACh quanta) due to temporal dispersion of the transmitter secretion process was 43% at τMEPC=1.0 msec and 20% at τMEPC=4–5 msec under conditions when acetylcholinesterase (AChE) was inhibited. When τMEPC varied over a wide range, the effect of the EPC amplitude loss could be described by a curve with steeply and gently sloping portions; the boundary between these two portions corresponded to approximately 1.0 msec τMEPC, which is nearly the channel “lifetime” at resting membrane potential. The rise time of the EPC only slightly related to changes in τMEPC. The rate of EPC decay exceeded that in MEPC only when the “lifetimes” of the ACh-activated ionic channels were lower than their physiological values. In this case, the kinetics of transmitter release became a factor determining the EPC decay time course. Three variants of an increase in temporal dispersion of the ACh quanta secretion were modeled for constant τMEPC: one resulting from an increase in the SPD rising phase; a second resulting from equal increases in the SPD rising and declining phases, and a third resulting from an increase in the SPD declining phase. The results of the first variant corresponded most closely to experimental data on changes in EPC during a short-term period of rhythmical activity. This was also characterized by minimal effect of EPC amplitude loss. It has been suggested that the interrelation between the parameters of SPD and τMEPC is an important factor regulating the amplitude and duration of the postsynaptic signal. The maintenance of this interrelation at a constant level ensures reliability of synaptic transmission.
TL;DR: Activity of single neurons and mass evoked potentials (EP) were recorded from the auditory and associative cortices in acute experiments on rats anesthetized with urethane, nembutal, or chloralose; pure tones were used as acoustic stimuli.
Abstract: Activity of single neurons and mass evoked potentials (EP) were recorded from the auditory (area 41) and associative (area 39) cortices in acute experiments on rats anesthetized with urethane, nembutal, or chloralose; pure tones were used as acoustic stimuli. The EP appearing in response to a wide range of sound tones on the surface of the auditory and associative cortices were dissimilar in their latency and shape. For neurons exhibiting stable responses, the frequency-threshold curves (FTC) were plotted.
TL;DR: It has been found that the spatial distribution of the nerve impulse-evoked transmitter secretion along each terminal branch is complex: the secretion increases distalward along the proximal by nearly a third of the terminal length and decreases linearly along its more distal portions.
Abstract: Nerve terminals with different length of their branches and with different types of ramification have been studied in the experiments performed on frog cutaneous-pectoralis muscle using electrophysiological and morphological techniques. It has been found that the spatial distribution of the nerve impulse-evoked transmitter secretion along each terminal branch is complex: The secretion increases distalward along the proximal by nearly a third of the terminal length and decreases linearly along its more distal portions. An increase in terminal length is followed by distalward shift of the secretion peak, by more gradual decay in the secretion if plotted along distal portions of the terminal, and by a decreased contribution of the secretion from distal portions to total secretion from the terminal. The critical terminal length at which total secretion from the terminal reached its maximum has been estimated. The distalward decrease of a secretion along the secondary terminal branches is similar to that found in the distal portion of the main terminal branch next to the ramification knot. An increase in terminal length and in the number of branchings is followed by decreased conduction velocity and transmitter release synchronism. The mechanisms determining limitations of the terminal length and the appearance of secondary terminal branches are discussed.
TL;DR: It is shown that the neurons significantly more often decrease their excitatory responses to the associated action of transmitters, and that responses are not enhanced.
Abstract: The probability, direction, and intensity of changes in mean firing rate of spike activity elicited by application of L-glutamate (Gl) and acetylcholine (ACh) have been compared in a series of successive responses of neuronal units in the sensorimotor cortex of unanesthetized rats; delayed paired application of the above transmitters was used. It is shown that the neurons significantly more often decrease their excitatory responses to the associated action of transmitters, and that responses are not enhanced. In the population of neurons studied, decreases in responsiveness with respect to Gl and ACh occurred with the same probability and in similar fashion over the whole period of testing (60 applications). After long-term transmitter application, potentiation became more typical of the responses to Gl than to ACh.
TL;DR: The neurotrophic control disturbance arising when the axonic flow is blocked by colchicine led to intensification of active chloride transport, increase in the intracellular Cl− concentration, and decrease in the equilibrium chloride potential, which resulted in a denervation-like depolarization of the muscle membrane.
Abstract: Experiments on innervated fibers of the diaphragmatic muscle of rat led to the conclusion that the furosemide-sensitive chloride transport is inactive under normal conditions due to the depressing effect of the substances transferred to the muscle by fast axoplasmic transport. The neurotrophic control disturbance arising when the axonic flow is blocked by colchicine led to intensification of active chloride transport, increase in the intracellular Cl− concentration, and decrease in the equilibrium chloride potential, which resulted in a denervation-like depolarization of the muscle membrane.
TL;DR: Both inhibitory and excitatory influences on spike activity of inspiratory and expiratory neurons were found, with suppression effects being markedly predominant, and possible mechanisms underlying the realization of thalamorespiratory influences are discussed.
Abstract: The effects of rhythmical low- and high-frequency stimulation of specific nonsensory anterior ventral and associative mediodorsal thalamic nuclei (AV and MD, respectively) on the activity of neuronal units in the medullary ventral respiratory nucleus were studied in acute experiments on anesthetized, spontaneously breathing cats. Both inhibitory and excitatory influences on spike activity of inspiratory and expiratory neurons were found, with suppression effects being markedly predominant. Thresholds for inspiratory neuronal responses were lower as compared with those for expiratory cells. Electrical AV stimulation mainly produced an inhibitory effect on the activity of nonspecific reticular neurons (without respiratory activity), whereas during MD stimulation activating effects on these neurons dominated. Possible mechanisms underlying the realization of thalamorespiratory influences are discussed.
TL;DR: An analysis of crossed interval histograms for a pair of neurons located in the same microvolume of the cortex has revealed the existence of two independent postsynaptic effects of LC stimulation: a “fast” (synaptic) effect and a ‘slow’ (modulatory) effect.
Abstract: The effects exerted by electrical stimulation of the locus coeruleus (LC) on neuronal activity in the visual cortex have been studied in acute experiments on rabbits. The pattern of cortical afterprocesses affecting poststimulus histograms of neuronal activity has been found not always to correspond to the direction of change in the neuronal excitation level in the period of LC stimulation. An analysis of crossed interval histograms for a pair of neurons located in the same microvolume of the cortex has revealed the existence of two independent postsynaptic effects of LC stimulation: a “fast” (synaptic) effect and a “slow” (modulatory) effect. The findings are discussed with allowance for morphological features of the synaptic connections and interneuronal transmission in the noradrenergic system of the brain.
TL;DR: Application of serotonin (5-hydroxytryptamine; 5-HT) to rat dorsal root ganglion neurons under conditions in which potassium conductance was blocked by cesium ions elicited depolarizing responses followed by an increase in membrane conductance did not exhibit desensitization.
Abstract: Application of serotonin (5-hydroxytryptamine; 5-HT) to rat dorsal root ganglion neurons under conditions in which potassium conductance was blocked by cesium ions elicited depolarizing responses followed by an increase in membrane conductance. The responses did not exhibit desensitization and were due to activation of 5-HT receptors of the third type (5-HT3Rs), since they were insensitive to methysergide, the 5-HT2R antagonist, but were inhibited by tropicetrone (ISC 205–930) and metoclopramide, the 5-HT3R antagonists. The reversal potential of the 5-HT-induced depolarizing responses was −11.9 mV; their amplitude decreased following a decrease in extracellular Na+ concentration but remained constant after intracellular injection of GTP. The amplitude of the responses increased following elevation of intracellular cAMP concentration caused by theophylline or sodium fluoride whose potentiating effect was reduced by butamide, a protein kinase A inhibitor. Potentiation of the 5-HT-induced responses was also produced by increased intracellular Ca2+ concentration following either direct intracellular injections or a burst of action potentials. The potentiation could be prevented by trifluoroperazine, the calmodulin inhibitor. The 5-HT effects were also potentiated by methylfurmetide, an activator of muscarinic acetylcholine receptors. The effect of methylfurmetide was slightly decreased by trifluoroperazine and was markedly decreased by polymixin B, a protein kinase C inhibitor. The effects of 5-HT were also enhanced by ethanol.
TL;DR: The effect of extra-high frequency electromagnetic radiation on the development of organotypical culture of the spinal ganglia of a 9–10 day-old chick embryo was investigated and the possibility of using the stimulating effect of EHF EMR in medical practice for intensifying regeneration in pathology and after trauma of the peripheral nervous system is discussed.
Abstract: The effect of extra-high frequency electromagnetic radiation (EHF EMR) on the development of organotypical culture of the spinal ganglia of a 9–10 day-old chick embryo was investigated. EMR with a wavelength of 5.6 mm and a rate of flow density 100 mW/cm2 was used. The stimulating action of EMR at rate of flow density of 4.0 mW/cm2, manifested in intensification of the growth of neurites of sensory neurons and the proliferation of the peripheral glia, was observed. EHF EMR with a density >100 mW/cm2 exerted inhibitory influence. The possibility of using the stimulating effect of EHF EMR in medical practice for intensifying regeneration in pathology and after trauma of the peripheral nervous system is discussed.