Spreading depression produced in the thalamus,hippocampus, and caudate nucleus by electrical stimulation of the parietal cortex in rats

The parameters of cortical electrical stimulation (ES) producing synaptically-operated spreading depression (SD) were determined in rats. Waves of SD were regularly triggered in the thalamus by brief, high frequency ES (0.02–0.05 sec; 200–500 Hz) of the parietal cortex. Monitoring by EEG confirmed the lack of accompanying convulsive activity in the cortex and the subcortical structures investigated. Use of Nembutal-induced anesthesia led to a higher minimum threshold for onset of SD, without preventing short-latency thalamid SD. Stimulating the parietal cortex was less effective for synaptic excitation of hippocampal and caudate SD. Hippocampal, unlike thalamic SD, was accompanied by spells of epileptiform activity, most pronounced at certain points in the onset and decline of the SD wave. These brief convulsive episodes were not the cause but the result of SD to a large extent. The low, subconvulsive threshold of synaptically triggered subcortical as well as cortical structures should therefore be taken into account when considering the functional significance of the SD reaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 36–44, January–February, 1990.     

Dynamic thermal mapping of rat brain during sensory stimulation and spreading depression

Using both techniques of thermovision and statistical analysis of thermal imaging, dynamics of temperature distribution over the dorsal surface of the brain were investigated through the intact skull during acute experiments on white rats. Both diffuse and regionally specific cerebral thermal reactions were observed during visual, acoustic, and somatosensory stimulation, together with multiple local thermal response, often following a specific pattern. These outline thermal effects differing from the compartment of the brain to another in degree, stability, and point of onset. Temperature waves developed together with spreading depression, produced in the cortex by injecting KC1. Once investigations had been performed this response could be divided into diffuse and spatially ordered components. The possible mechanisms of this thermal imaging of brain processes are discussed, together with how they are linked with changes in cerebral blood flow and neuronal metabolic thermal production.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Institute of Radio Engineering and Electronics, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 26–35, January–February, 1986.     

Spread of fast thermowaves through the cerebral cortex produced by visual stimulation

Thermowaves spreading through the cerebral cortex were observed and investigated during acute experiments on white rats using a new technique — that of thermoencephaloscopy (TES) through the intact skull. These waves were induced by regular visual stimulation (at intervals of 1.5–3 min) or by initiating one of the flashes and spread through the cortex along trajectories of five basic types; amplitude of thermowaves: 0.005–0.1°C; length: 10–15 mm; duration 1.2–11.4 sec; velocity: 1–33 mm/sec; extent of pathway: 2–56 mm. They appeared with a high degree of probability (of 0.92) during the interval between 15 sec before and 26 sec after the flash. Numbers of moving waves declined by the point of stimulus application and rose by 7–8 sec after the flash. Waves arose in 50% of cases in the contralateral visual cortex (areas 17 and 18a), spreading to the midline and crossing to the ipsilateral hemisphere (areas 17, 18a, and 7). Local waves moving along a circular trajectory were also discovered in the contralateral visual cortex. Several types of wave, differing in trajectory, also arose in the ipsilateral visual cortex. Mechanisms and possible significance of this effect are examined.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 467–475, July–August, 1989.     

Cortical spreading depression synaptically induced by brief high-frequency electrical stimulation of the rat brain

Electrical stimulation (ES) at the surface of the rat brain (10–200 Hz; brief trains of 10 pulses) was found to be most effective for evoking waves of spreading depression (SD) in the cortex. Repeated stimuli spaced at 10–15 min intervals did not produce convulsive activity and nor did mechanisms of SD inhibition set in under these conditions. A 5–6-fold reduction in SD threshold occurred when the intra-burst rate was increased from 10 to 200 Hz. Temporal summation of residual processes occurring with suprathreshold ES applied at the rate of 50 and 200 Hz resulted in significant broadening of the SD focus in the ES area and regular occurrence of additional SD foci on the side ipsilateral to stimulation and in the contralateral cortex. The protracted changes in cortical excitation lingering after ES by high-frequency currents brought about a decline in SD threshold and pointed to the active part played by synaptic processes in triggering this reaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 789–796, November–December, 1989.     

Effects of the γ-aminobutyric acid antagonist disulfotetraazaadamantane on evoked neuronal response in hippocampal slices

The effects were investigated of disulfotetraazaadamantane (DSTA), a blocker of -aminobutyric acid, on summated potentials in field CA 1 of the mouse hippocampus arising in response to electrical stimulation of Shaffer's collateral. At a concentration of 5·10^–6–10^–5 M, DSTA led to a considerable increase in the amplitude of the main population spike (PS) and the onset of additional PS. The effects induced by DSTA resembled those observed following picrotoxin application, which it exceeded two- to threefold in intensity, however. Findings are reviewed from the standpoint of the effects exerted by the test substance on synaptic processes in the hippocampus in vitro.Institute of Physiologically Active Substances, Academy of Sciences of the USSR, Chernogolovka, Moscow Oblast. Institute of Brain Research, National Scientific Mental Health Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 1, pp. 66–70, January–February, 1989.     

Influence of picrotoxin and duration of conditioning on the induction of associative long-term potentiation in the mouse hippocampal area CAl in vitro

Field potentials (FP) induced in the radial layer of area CAl by stimulating Schaffer's collaterals (C2) were recorded in murine hippocampal slices and associative long-term potentiation (ALP) produced by combined tetanization of C2 and another group of fibers (C1) was investigated. The effects of simultaneous (C1 and C2) and successive activation (with C1 preceding C2 by 200 msec) of the two inputs were compared. Tetanization preceded by activation of C1 ("conditioning" input) was more effective in experiments with short (30 msec, 100 Hz) trains of stimuli. Tetanization with simultaneous activation of the two inputs as well as tetanization of C1 input by prolonged (150 msec) spike trains with inhibition were blocked by 5·10^–6 M picrotoxin. It is suggested that ALP induced by short trains of stimuli succeeding at 200 msec intervals serves as a more suitable model of memory than that induced by prolonged trains (of 1 sec).Brain Research Institute, National Mental Health Research Center, Academy of Sciences of the USSR, Moscow. Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 215–223, March–April, 1990.     

Modular organization of callosal neurons in the rabbit sensomotor cortex

The density of distribution of callosal neurons in the rabbit sensomotor cortex was studied by injecting horseradish peroxidase into the symmetrical region of the cortex. The degree of inequality of distribution of labeled neurons was determined visually and by statistical analysis. Stained callosal neurons were mainly small and medium-sized pyramidal cells, located chiefly in layer III–IV, and substantially less frequently in layers V and VI. Different forms of grouping of labeled neurons were observed in layer III–IV: two cells at a time, five to eight cells arranged vertically, or in concentrations, whose width was usually 120–200µ, and separated by areas with reduced density. The results are regarded as confirmation of those drawn previously from results of electrophysiological investigations on the modular organization of callosal connections in the rabbit sensomotor cortex.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Brain Institute, Academy of Medical Sciences of the USSR, Moscow. I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 451–457, July–August, 1984.     

Formation of "caudate spindles" in the rabbit sensomotor cortex during ontogeny

Electrical activity of the sensomotor and visual areas of the neocortex during stimulation of the caudate nucleus was recorded in young rabbits aged 3–60 days and in adults. Single stimulation of the caudate nucleus was found to cause the appearance of characteristic bursts of spindle-like rhythmic activity ("caudate spindles"), described previously in cats and monkeys, in the adult rabbit cortex. The latent period of the caudate spindle was about 200 msec, its duration 1–3 sec, and the frequency of its oscillations of the order of 12 Hz. Caudate spindles were most marked in the sensomotor cortex of the ipsilateral hemisphere. In rabbits under 10 days old caudate spindles were not found even if the intensity of stimulation was increased many times. Starting from the age of 15 days bursts of rhythmic activity resembling caudate spindles, but with lower frequency (about 8 Hz), longer latent period (up to 350 msec), and also with a higher threshold, appeared in the sensomotor cortex. The definitive type of caudate spindles was established toward the end of the first month of postnatal life, corresponding to the time of formation and complication of conditioned-reflex activity in developing animals.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 11–15, March, 1985.     

Phase relationships of cortical potentials in rabbits in different functional states

Phase shifts in EEG potentials were investigated in the rabbit cortex during photic stimulation and in controls. Degree of phase shift in the predominating theta waves was found to increase gradually with increasing distance between recording electrodes both with and without photic stimulation, pointing to the existence of a phase gradient — the conditions appropriate to the greater proportion of motor reactions. Photic stimulation induces an increase in numbers of non-phasic EEG waves recorded from close-lying sites as well as reduced scatter in levels of phase shift between EEG of the sensorimotor and visual cortex, thus rendering phase shifts more stable. Irradiation of excitation from the visual to the motor analyzer in response to photic stimulation occurs against a background of high correlation coefficient and coherent function levels and with a phase shift from 0 to 10–11°.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR. Moscow. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 507–513, July–August, 1989.     

Neurite growth and formation of connections in pteropodial mollusk neurons in culture

Neurons from the peripharyngeal nerve ring detached from the pteropodial molluskClione limacina were cultured in polylysine prepared in a 25% Leibovitz saltwater medium containing 2% embryonic calf serum. Neurite outgrowth was observed in a proportion of the neurons, reaching its peak rate during the first three days. Neurites grew up to 300 µm in length. Membrane potential of the neurons measured 40–60 mV. The latter generated either single action potentials or volleys of spikes. Neural connections between 70 pairs of cells with overlapping neurites were investigated on days 3–4. An electrical connection was discovered between cells in 20% of the pairs examined and, in 6%, stimulating one neuron of a pair produced an inhibitory postsynaptic potential in the other.Institute of Information Transmission Research, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 81–86, January–February, 1987.     

Immediate and remote postactivation effects in the human motor system

Postactivation effects consisting of protracted involuntary muscular contraction after 30–60 sec sustained voluntary effort were investigated. It was found that postactivation effects may be observed at the proximal muscles (uninvolved in the voluntary activity) following distal muscle contraction. Testing the state of muscles by the vibration activity of the muscle receptors showed that concealed changes persisting for 15–20 min occur apart from the direct postactivation effects already known. The point is made that postactivation phenomena reflecting the operation of certain central tonogenic structures activated by a voluntary effort or an increased afferent inflow may successfully be used in the study of postural control mechanisms.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 3, pp. 343–351, May–June, 1989.     

Suppression of associative long-term potentiation in the hippocampus after tetanization of reinforcing afferents

Field potentials (FP) induced in area C1 by gentle orthodromic stimulation were recorded in murine hippocampal slices and associative long-term potentiation (ALTP) produced by C2 tetanization associated with intensive tetanization of another group of fibers (C1) was investigated. A comparison was made between the effects of additional C1 tetanization produced at 50–300 msec before and after combined tetanization of both afferents. Where these intervals measured 50–200 msec, preliminary tetanization of C1 suppressed ALTP (rise in FP amplitude: 10.4±5.2%) in comparison with the regimen whereby additional C1 tetanization came later (giving a rise of 32.4±5.3%); no significant difference was noted at an interval of 300 msec. The three possible reasons for ALTP suppression are discussed, namely: inactivation of "fast" calcium channels, post-activation hyperpolarization of postsynaptic neurons, and synaptic inhibition. The ALTP suppression mechanism is thought to resemble that underlying the relative inefficacy of "reversible" combinations in the shaping of behavioral conditioned reflexes.Institute for Brain Research, Academy of Medical Sciences of the USSR, Moscow. Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 5, pp. 636–643, September–October, 1989.     

Conduction velocity and excitability of A and C fibers of cat mesenteric nerves

The conduction velocity and excitability of fibers running from the mesenteric into the splanchnic nerves were studied in experiments on cats. Among the A fibers of these nerves there were shown to be: 1) fibers with an excitation threshold of 0.06–0.10 V (stimulus duration 0.1 msec) and a maximal conduction velocity of 48–85 m/sec; 2) fibers with an excitation threshold of 0.3–0.7 V, impulses of which form up to five waves in the composition of the action potential, with maximal conduction velocities of between 8–10 and 33–39 m/sec; 3) fibers with an excitation threshold of over 1 V and a conduction velocity of between 1.8 and 7 m/sec. The excitation threshold of the group C fibers was 6–8 V. Impulses of these fibers form a low-amplitude wave in the composition of the action potential of the mesenteric and splanchnic nerves with a conduction velocity of 1.0–1.8 m/sec, several waves of higher amplitude with a conduction velocity of 0.5–1.2 m/sec, and several low-amplitude waves with a conduction velocity of 0.35–0.55 m/sec. The results of experiments with different combinations of arrangement of the stimulating and recording electrodes on the mesenteric and splanchnic nerves indicate that sympathetic postganglionic C fibers of the mesenteric nerves occur only in the second group, whereas afferent C fibers occur in all three of the groups distinguished.Institute of Normal and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 7, No. 3, pp. 272–278, May–June, 1975.     

Neuronal response produced in the human thalamic nucleus reticularis by significant and non-significant verbal and sensory stimuli

Response recorded by microelectrode techniques during the course of 46 stereotaxic operations on dyskinesia patients was investigated in 340 units of the nucleus reticularis (rt) of the human thalamus. Differences were found between the multistage response of three types of rt neurons (A, B, and C) to verbal (or acousticcum-sensory) functionally significant stimuli (FSS) at both the stage of stimulus presentation and during the performance of goal-directed motion. Phasic activation produced by FSS presentation (as well as onset and execution of movement) in 102 out of 183 type A cells (or 55.7%) was characteristic of these cells, combined with inhibition of B type neurons in 82 out of a 139 sample (or 59.0%) produced by FSS and at the preparatory as well as the execution stage of movement. Activity of type C neurons remained unchanged. A correlation was revealed between response in A and B cells and "excitatory" trigger stimuli, but no specificity with respect to physical or semantic parameters of verbal signals. A correlation occurred during the course of movement performance with somatosensory afferents without any specific relationship to type and somatotopic aspects of movement. The time-related dynamics of A and B cell response is thought to illustrate the interaction of two neuronal subsystems within the rt participating in the performance of goal-directed motor performance triggered by speech.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Institute of Neurosurgery, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 4, pp. 441–451, June–July, 1990.     

Comparison of direct influences of the perforant path on hippocampal CA1 and CA3 neurons in vitro

The efficiency of synapses of the perforant path located on terminals of apical dendrites of CA₁ and CA₃ neurons was investigated in sections of the guinea pig hippocampus in vitro. Neurons of both areas were shown to respond to stimulation of the perforant path by action potential generation. Responses of most CA₁ neurons appeared to repetitive stimulation with a frequency of up to 30–80/sec. Neurons in area CA₃ respond only to low-frequency stimulation (under 5/sec). Posttetanic potentiation of responses to stimulation of the perforant path was found in both areas of the hippocampus.Institute of Biophysics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 11, No. 4, pp. 303–310, July–August, 1979.     

Characteristics of background unit activity in the nucleus reticularis of the human thalamus

Background firing activity was examined in 240 neurons belonging to the thalamic nucleus reticularis (Rt) in the unanesthetized human brain by extracellular microelectrode recording techniques during stereotaxic surgery for dyskinesia. The cellular organization of Rt was shown to be nonuniform, and distinguished by the presence of three types of neuron: one with arrhythmic single discharge (A-type, 40%), another with rhythmic (2–5 Hz) generation of short high-frequency (of up to 500/sec) burster discharges (B-type, 49%) and a third with aperiodic protracted high-frequency (of up to 500/sec) bursting discharges separated by "silent" intervals of a constant duration of 80–150 msec (i.e., C-type, 11%). Differences between the background activity pattern of these cell types during loss of consciousness under anesthesia are described. Tonic regulation of neuronal type was not pronounced but a tendency was noticed in the cells towards a consistent rise in firing rate, rhythmic frequency and variability, etc. in both A and B units, especially in the latter. Findings pointing to the absence of a direct relationship between rhythmic activity in the Rt and parkinsonian tremor were confirmed. Background activity in B-type cells was found to increase and then stabilize with a rise in the degree of tremor. The nature of regular bursting activity patterns in B and C neurons is discussed in the light of our findings.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Institute of Neurosurgery, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 456–466, July–August, 1987.     

Quantitative morphological charateristics of developing neurons of the brain-stem reticular formation

Two types of neurons — reticular (with few branches) and multipolar giant (densely ramified) were distinguished in the brain-stem reticular nuclei of the brain in Golgi preparations from cat fetuses aged 45–55 days and kittens aged 1–5 and 30 days. The quantitative morphological characteristics of these neurons at different stages of development were determined from the dimensions of their bodies, the number, length, and ramification of their dendrites, and the overall ramification of the cell. The types of neurons described above differed in both qualitative and quantitative indices and in the character of their maturation. Maximal ramification of dendrites of giant multipolar neurons was observed in the embryonic period. Foci of maximal ramification in reticular neurons were close to the cell bodies. In gaint multipolar neurons in fetuses and 30-day-old kittens foci of maximal ramification were located on the proximal and distal portions of the dendrites, but in the newborn kittens on the proximal segments only. These facts are examined in connection with differences in the spike activity of the growing neuron.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 53–61, January–February, 1980.     

Stationary-kinetic model of noradrenaline secretion autoregulation by adrenoceptors

The process of noradrenaline secretion regulation by autoreceptors is described in terms of stationary-kinetic response. Principal constants of this response are determined using the author's own data. A number of findings in the literature used to support the theory of autoregulation of noradrenaline secretion by autoreceptors could be adequately explained by analyzing the model adopted, which may thus be considered a stationary-kinetic theory of noradrenaline secretion regulation by adrenoceptors.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Institute For Research on Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 20, No. 3, pp. 301–309, May–June, 1988.     

Background activity of neurones of the amygdaloid complex and its changes in response to hippocampal stimulation

The background activity of neurones of the amygdaloid complex (AC) and changes induced in it by stimulation of the fimbria and adjacent regions of the hippocampus were recorded by means of microelectrodes. Background activity of 40% of the neurones of the AC consisted of an irregular spike discharge, while that of 10% was regular. The remaining neurones showed a tendency to group discharges. High-frequency hippocampal stimulation at 200 pulses/sec inhibited activity of 37% and facilitated activity of 23% of the neurones. Responses began 20–300 msec after the onset of stimulation. Low-frequency stimulation at 0.5–8 pulses/sec facilitated discharges in 42.6% of neurones. The results obtained are discussed in relation to the influence of the hippocampus on AC activity.Institute of Physiology, Siberian Branch of the Academy of Sciences of the USSR, Novosibirsk. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 500–504, September–October, 1971.     

Investigation of the frequency of impulse discharges of human motoneurons during voluntary muscle contraction

The motor unit (MU) potentials of the human m. rectus femoris were recorded during voluntary isometric contraction by means of a bipolar needle electrode. The frequency of impulse discharge of individual motoneurons was defined as a quantity inverse to the average interval between impulses during 0.5 or 1.0 sec. The force of contraction varied from 0 to 4–14 kg (17–47% of the maximum). The investigations showed that in addition to switching on and off of motoneurons during a change of contraction force, the frequency of their impulse discharges also changes. Motoneurons recruited at a low force (low-threshold) reached the highest frequency (up to 18–21 impulses/sec). As a rule, the higher the threshold, the lower the frequency in the entire range of changes. In the case of prolonged contraction with a constant force the frequency of discharges dropped during the first 1–2 min. The established frequency level did not exceed 10–13 impulses/sec. A voluntary increase of contraction force at this period was related with a new increase of frequency. Recruitment of new motoneurons was observed during prolonged contraction. The data obtained show that the mechanism of change of the firing frequency of motoneurons actively participates in contraction gradation, mainly its dynamic component. It is regarded as a mechanism of smooth and precise control. The decrease of frequency during prolonged contraction is apparently due to adaptation, although the participation of inhibition is not precluded.Institute of Problems of Information Transmission, Academy of Sciences of the USSR. Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 200–209, March–April, 1971.