Effects of intracellular injection of chloride ions on inhibitory postsynaptic potentials and postburst hyperpolarization in cat sensorimotor cortex neurons

It was shown during acute experiments on cats immobilized with myorelaxants that intracellular injection of chloride ions into both pyramidal and non-pyramidal neurons of the sensorimotor cortex produces the early component only of IPSP, while the late phase and postburst hyperpolarization of pyramidal neurons are not very sensitive to this effect. It is deduced that membrane permeability to chloride ions increases during the early component of IPSP in pyramidal and nonpyramidal neurons of the cat sensorimotor cortex, while the late phase and postburst hyperpolarization is less dependent on chloride permeability.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 453–460, July–August, 1986.     

Corticofugal postsynaptic influences on red nucleus neurons

The responses of red nucleus neurons to stimulation of the sensorimotor cortex was studied on nembutal-anesthetized cats. Most of the rubrospinal neurons were identified according to their antidromic activation. Stimulation of the sensorimotor cortex was shown to evoke in the red nucleus neurons monosynaptic excitatory potentials with a latency of 1.85 msec, polysynaptic excitatory potentials (EPSP), and inhibitory postsynaptic potentials (IPSP) with a latency of 9–24 msec. The EPSP often produced spikes. The probability of generation of spreading excitation is greater with motor cortex stimulation. The monosynaptic EPSP are assumed to arise under the influence of the impulses arriving over the corticorubral neurons as a result of excitation of axodendritic synapses. The radial type of branching of red nucleus neurons facilitates the transition from electrotonically spreading local depolarization to an action potential triggered by the initial axonal segment. Polysynaptic EPSP and IPSP seem to be a result of activation of fast pyramidal neurons whose axon collaterals are connected via interneurons with the soma of the red nucleus neurons.L. A. Orbeli Institute of Physiology of the Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 1, pp. 43–51, January–February, 1971.     

Aspects of synaptic reorganization in the cat sensorimotor cortex after lesion of the symmetrically contralateral hemisphere

During the course of acute experiments, response in cortico-spinal neurons (CSN) to stimulating the ipsilateral ventral thalamic nucleus was investigated by extracellular recording techniques in intact adult cats and others with lesioning inflicted on the contralateral sensorimotor cortex 6–18 months previously. An accelerated stage of growth was noted in monosynaptic IPSP and CSN with slow-conducting axons in animals with surgically-induced lesion, suggesting reorganization of synaptic contacts within the CSN somatodendritic membrane. The collision test was applied to make a complete examination of arborization and of other aspects of CSN axons, as well as the presence of collaterals running to the ventrolateral thalamic nucleus and helping to form the ipsilateral pyramidal tract. The significance is discussed of plastic synaptic rearrangement in the ipsilateral thalamo-cortical reverberating system for formation of the efferent spike train during partial interhemisphere cortical deafferentation.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 612–621, September–October, 1990.     

Modulation of pyramidal response in the rat sensorimotor cortex after combined stimulation of the lateral hypothalamus and the sensorimotor cortex

It was shown during experiments on unrestrained rats that rhythmic stimulation of the pyramidal tract produced a statistically significant increase in the functional activity of neuronal populations of the sensorimotor cortex, manifesting as potentiation of the primary, positive phase of pyramidal cortical response. Combined rhythmically matched stimulation of the pyramidal tract and of the lateral hypothalamus leads to statistically significant enhancement in potentiation of the positive phase of pyramidal cortical response compared with effects produced independently of hypothalamic involvement. When stimulation of the pyramidal tract and the lateral hypothalamus are combined with stimulation applied at the same periodicity to the sensorimotor cortex, a further statistically significant enhancement in potentiation of the positive phase of pyramidal cortical response is seen in addition to the potentiating effect produced by hypothalamic stimulation.Institute for Brain Research of the All-Union Scientific Center of Mental Health, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 367–373, May–June, 1986.     

Molecular mechanisms underlying sensorimotor cortex pyramidal neuron involvement in the feeding behavior of rabbits

Response in pyramidal neurons belonging to the sensorimotor cortex (37% of total nerve cells investigated in this zone) which were identified by stimulating the bulbar pyramids, were investigated during experiments on unrestrained rabbits. Pyramidal neurons having connections with the lateral hypothalamus were activated during operation of feeding behavior, while activity was inhibited in those unconnected with the lateral hypothalamus. Microiontophoretic application of a protein synthesis inhibitor to pyramidal neurons caused their ability to respond to ascending activating influences from the lateral hypothalamus to disappear. When pentagastrin was applied to these neurons following the protein synthesis blocker, they recovered their ability to participate in hypothalamic feeding reaction. It is suggested that synthesis and release of a gastrin-like peptide into the perineuronal space is required for sensorimotor cortex pyramidal neurons to participate in the organization of feeding behavior.P. K. Anokhin Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 5, 601–606, September–October, 1987.     

Action of strychine on evoked potentials and postsynaptic responses of cat sensomotor cortical neurons

Acute experiments on immobilized cats lightly anesthetized with pentobarbital showed that application of strychine to the cortical surface inhibits slow negative potentials arising during direct and primary responses of the sensomotor cortex and corresponding IPSPs in pyramidal neurons. Iontophoretic applications of strychine blocks predominantly the early component of the IPSP, during which the input resistance under normal conditions is significantly less than during the late component of the IPSP, indicating that these components differ in their genesis. It is concluded that individual components of cortical evoked potentials have a common genesis, and that the slow negative potential is the dipole reflection of the IPSP in pyramidal neurons; the early component of the IPSP, moreover, is generated as a result of activation of axo-somatic inhibitory synapses, whereas the late component is generated as a result of activation of axo-dendritic synapses. The mediators in these inhibitory synapses may be different.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 480–487, July–August, 1984.     

Intrathecal Delivery of IL-6 Reactivates the Intrinsic Growth Capacity of Pyramidal Cells in the Sensorimotor Cortex after Spinal Cord Injury

We have previously demonstrated the growth-promoting effect of intrathecal delivery of recombinant rat IL-6 immediately after corticospinal tract (CST) injury. Our present study aims to further clarify whether intrathecal delivery of IL-6 after CST injury could reactivate the intrinsic growth capacity of pyramidal cells in the sensorimotor cortex which project long axons to the spinal cord. We examined, by ELISA, levels of cyclic adenosine monophosphate (cAMP), adenylyl cyclase (AC, which synthesizes cAMP), phosphodiesterases (PDE, which degrades cAMP), and, by RT-PCR, the expression of regeneration-associated genes in the rat sensorimotor cortex after intrathecal delivery of IL-6 for 7 days, started immediately after CST injury. Furthermore, we injected retrograde neuronal tracer Fluorogold (FG) to the spinal cord to label pyramidal cells in the sensorimotor cortex, layers V and VI, combined with βIII-tubulin immunostaining, then we analyzed by immunohistochemisty and western blot the expression of the co-receptor gp-130 of IL-6 family, and pSTAT3 and mTOR, downstream IL-6/JAK/STAT3 and PI3K/AKT/mTOR signaling pathways respectively. We showed that intrathecal delivery of IL-6 elevated cAMP level and upregulated the expression of regeneration-associated genes including GAP-43, SPRR1A, CAP-23 and JUN-B, and the expression of pSTAT3 and mTOR in pyramidal cells of the sensorimotor cortex. In contrast, AG490, an inhibitor of JAK, partially blocked these effects of IL-6. All these results indicate that intrathecal delivery of IL-6 immediately after spinal cord injury can reactivate the intrinsic growth capacity of pyramidal cells in the sensorimotor cortex and these effects of IL-6 were partially JAK/STAT3-dependent.     

Effects of bicuculline and picrotoxin on fast and slow IPSP in pyramidal neurons in hippocampal slices isolated from the rat

The effects of different concentrations of bicuculline and picrotoxin on IPSP of pyramidal neurons with high and low rates of rise ("fast" and "slow" IPSP) were investigated in hippocampal slices isolated from area CA1. These neurons generated mainly fast IPSP in response to antidromic stimulation; orthodromic stimulation produced both fast and slow IPSP, often combining into a single IPSP with two phases. Both these patterns of IPSP were recorded from the apical dendrites as well as the soma and were reversibly inhibited by bicuculline and picrotoxin. Degree of inhibition depended on dose and duration of blocker action, but slow IPSP were more resistant to this action. At the same effective concentration of bicuculline or picrotoxin, slow IPSP were inhibited later and recovered sooner after washout of blocker than fast IPSP. The difference between the inhibitory effect of blockers on fast and slow IPSP persisted under tetanic stimulation, although the progress of reduction in IPSP proceeded far more rapidly than following application of a single stimulus. The reason for this phenomenon is discussed, as well as particular features of -aminobutyric acid (GABA) receptors of pyramidal neurons mediating generation of slow IPSP.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 44–54, January–February, 1990.     

Inhibition in the fish olfactory bulb

Inhibition in the olfactory bulb of the carp was studied by recording potentials from secondary neurons intracellularly. Three types of inhibition — trace, early, and late — can arise in neurons of the olfactory bulb. Trace inhibition corresponds to hyperpolarization about 20 msec in duration, which is closely connected with the spike, but it is not after-hyperpolarization but an IPSP. Early and late inhibition correspond to IPSPs of different parameters. The first has a latency of 0–50 msec (relative to the spike) and a duration of 60–400 msec; the corresponding values for the second are 100–400 msec and 0.5–3 sec. The possible mechanisms of these types of inhibition are discussed.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 650–656, November–December, 1971.     

Disturbances in Formation of the New and Old Cortex at Changes of Conditions of Embryonic Development

Using a model of acute hypoxia during pregnancy of rats, changes in the development of old (hippocampus) and new (sensorimotor) cortex associated with disturbance of neuronogenesis have been revealed in the studied brain structures at the period of action of a pathological factor. It was found that in rats submitted to hypoxia at the 13–14th days of embryogenesis, the number of degenerating neurons (including the pyramidal ones) at various levels of chromatolysis increased since the 5th day after birth; the increase was present for the entire first month of postnatal development. In the cortex of rat pups submitted to prenatal hypoxia there were observed deformation of neuronal bodies, vacuoles in the cytoplasm, shrinkage of apical dendrites of pyramidal neurons and delayed development of the structure (time of the appearance of spikes, formation of structural elements and the size of the cells) of the nervous tissue of the brain of the rat pups exposed to prenatal hypoxia. The columnar structure of the cortex was disturbed. In hippocampus, the process of degeneration of neurons started by 2–3 days later than in the cortex; by two weeks of postnatal development a massive degeneration and death of a part of neurons were also revealed. The morphometrical analysis showed a decrease in the number of neurons and their total area in the sensorimotor cortex (the layer V) and an increase in the number of glial elements at the 10–17th days after birth. In the hippocampus a decrease in the area occupied by neurons and in their size was detected in adult animals. The adult rats submitted to prenatal hypoxia were found to have disturbances of memory and learning. A correlation was shown between the disturbances of the conditions of embryonic development and the changes in the ability of learning and storage of new skills in the offspring.     

Characteristics of inhibition in the kitten sensory-motor cortex

Responses of 340 neurons of the sensory-motor cortex to electric shocks applied to the limbs were investigated in kittens aged 3–30 days. In 9.4% of cells of kittens aged 3–10 days and in 17.1% of cells in kittens aged 21–30 days pauses were observed immediately after the excitatory component of the extracellular response. Intra- and quasiintracellular recording showed that postsynaptic inhibition participates in the genesis of these pauses. The IPSPs which, as a rule, followed the excitatory component of the response were of much longer duration (up to 250–380 msec) than the analogous IPSPs in the sensory-motor cortex of adult cats. Usually the amplitude of the IPSP in kittens did not exceed 5 mV.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 227–231, May–June, 1977.     

Self-sustained rhythmic spike and wave activity and response of glial and nerve cells in the cat sensorimotor cortex

During acute experiments on unanesthetized cats, immobilized with myorelaxants, it was found that during rhythmic stimulation (8–14 Hz, duration: 10 sec) of the ventroposterolateral thalamic nucleus brief hyperpolarization is succeeded by depolarization in the pyramidal neurons of the sensorimotor cortex. Following this depolarization, rhythmic (approximately 3 Hz) paroxysmal depolarizing shifts in membrane potential are produced by ending stimulation, succeeded by protracted hyperpolarization and termination of rhythmic wave activity. Depolarization only is observed in glial cells, however, while hyperpolarization sets in after hyperpolarization is completed in the neurons. It is suggested that long-term changes in the membrane potential of cortical cells could make some contribution to the setting up and termination of rhythmic spike and wave activity.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 319–325, May–June, 1986.     

Inhibition in hippocampal pyramidal neurons during peripheral stimulation

Responses of hippocampal pyramidal neurons were investigated intracellularly in unanesthetized rabbits immobilized with tubocurarine. A single stimulus, applied to the sciatic nerve, evoked prolonged (up to 2.5 sec) hyperpolarization of the cell membrane, accompanied by inhibition of action potentials. The latent period of the evoked hyperpolarization was 48±16.4 msec, and its amplitude 2.5±1.9 mV. In some neurons the development of hyperpolarization potentials was preceded by excitation. The suggestion is made that hyperpolarization of the membrane of pyramidal cells during peripheral stimulation is manifested as an inhibitory postsynaptic potential (IPSP), generated with the participation of hippocampal interneurons. The possibility of prolonged tonic action of interneurons from outside as a cause of prolonged inhibition of the pyramidal neurons is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 3, pp. 278–284, November–December, 1969.     

Postsynaptic potentials of neurons of the cat auditory cortex

The electrical reactions of 294 neurons of the auditory cortex to a click were recorded in experiments on cats immobilized with tubocurarine (174 intra- and 120 extracellularly). The value of the membrane potential varied from 30 to 70 mV with intracellular leads. The following types of reactions were obtained (the number of neurons is given in parentheses): a peak without slow oscillations in the membrane potential (4), EPSP (3), EPSP-peak (6), EPSP-peak-IPSP (17), EPSP-IPSP (9), primary IPSP (114, including 23 with an after-discharge). Twenty one neurons did not react to a click. The amplitude of the sub-threshold EPSP was 1–1.5 mV, the duration of the ascending part was about 10 and of the descending part 20–30 msec. The peak potential on the ascending part of the EPSP developed at the critical level of 3–4 mV. The amplitude of the peaks varied from several millivolts to 50–60. In 17 neurons prolonged hyperpolarization having all the properties of an IPSP, developed after the peak. The amplitude of these IPSP varied in different neurons from 1 to 10 mV and the duration varied from 20 to 80 msec. IPSP without preceding excitation of the given neuron were the predominant types of reaction. The latent period of these primary IPSP varied from 7 to 20 msec and the amplitude from 1 to 15 msec with a duration of 30–200, more frequently 80–100 msec. It is suggested that two types of inhibition develop in neurons of the auditory cortex in response to a click: recurrent and afferent. The functional significance of the first consists in limiting the duration of the discharge in the reacting neurons, the second prevents the development of excitation in adjacent neurons, thereby limiting the area of neuronal activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSSR, Kiev. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 339–349, July–August, 1971.     

Neurons and their interconnections in the frontal cortex of monkeys

It was shown by the Golgi and Golgi-Kopsch method that pyramidal cells of layers II–IV in the frontal cortex of the monkeyMacaca rhesus have numeruous, mainly recurrent axon collaterals by means of which they form vertical connections. Pyramidal cells with ascending axons are found. Axons of stellate basket neurons unite pyramidal cells in both horizontal (modules) and vertical (micromodules) directions; depending on the direction of the axon collaterals, two groups of stellate neurons can be distinguished. Groups of 14 to 16 pyramidal cells whose apical dendrites are connected into bundles were found. Axons of pyramidal cells in layers II–IV descend in the composition of the pyramidal tract and give off collaterals which run toward the bodies and dendrites of neighboring pyramidal cells, united into the same group, forming terminal and en passant junctions. Besides bundles, special kinds of "local" cell groups with U-shaped axons are found.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 15, No. 2, pp. 115–120, March–April, 1983.     

Neuronal composition and interneuronal connection of area 5 in the cat parietal association cortex

Area 5 of the cat cortex was studied by Nissl's method and by Golgi's chromate-silver impregnation method. Its typical six-layered structure with well-developed layers of pyramidal cells was revealed. The characteristic features of area 5 are: predominance of pyramidal cells in layers II–III and the presence of large forms (40×26 µ) among them (in layer III); giant pyramidal neurons (70×23 µ) arranged singly or nidally in layer V; large (diameter 25–30 µ) and giant (diameter 40–45 µ) stellate cells with radial dendrites, arranged singly or in groups in layers V–VI; infrequent efferent fusiform neurons (40×20 µ) in layers V–VI. Stellate cells connecting pyramidal neurons in the same or in different layers were found in layers II–VI. Some stellate cells in layers II–III form long horizontal connections within area 5. Interneuronal connections are effected by axosomatic and axodendritic terminals, the latter being more numerous; Dendrodendritic and axoaxonal synapses are less common.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 1, pp. 35–42, January–February, 1979.     

Laminar analysis of hippocampal potentials evoked by peripheral stimulation

From areas SA₁ and SA₂ of the dorsal hippocampus of unanesthetized rabbits immobilized with d-tubocurarine a laminar analysis was made of evoked potentials (EP) in response to stimulation of the sciatic nerves. Inversion of the initial surface-positive phase of the EP was observed at the level of the pyramidal layer. The subsequent surface-negative phase reached a maximum value in the layer of basal dendrites of the pyramidal cells. The initial portion was inverted somewhat above the pyramidal layer and reached its maximum value approximately at the boundary of the pyramidal and radial layers. The change in sign of the remaining portion of this component occurred 0.3–0.4 mm deeper than the pyramidal layer. It is suggested that both components of the EP picked up from the hippocampal surface are due to an excitatory postsynaptic potential (EPSP) at the apical (positive phase), and basal (negative phase) dendrites. The positivity in the region of the pyramidal somata appears to be an extracellular reflection of a composite postsynaptic potential (IPSP) generated in this region.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 4. pp. 434–438, July–August, 1970.     

Aspects of excitation and inhibition produced in parietal association cortex neurons by stimulating thalamic association nuclei

Neuronal response to single stimuli applied to the thalamic dorsolateral and posterolateral nuclei (DLN and PLN resepctively) was investigated in the parietal association cortex. Primary IPSP following DLN and PLN stimulation was noted in 62.5% and 79.6% of instances respectively. Latencies of EPSP and IPSP when stimulating the two nuclei were longer for the DLN. The amplitude of EPSP evoked by stimulating association nuclei rose and declined smoothly, while that of IPSP showed a fast rise and a more steady decline. The EPSP appearing during the evolution of IPSP were of higher amplitude than control level of resting potential. Both amplitude and duration of IPSP induced in a single unit by stimulating different association nuclei were extremely similar, thus confirming the involvement in this operation of the same inhibitory cortical interneurons. Duration of IPSP was shorter than that of inhibitory background spike activity. It is postulated that the discrepancy in duration can largely be ascribed to properties of the neurons themselves.State University, Odessa. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 529–536, September–October, 1991.     

Postsynaptic components of paroxysmal neuronal response in the strychninized neocortex

Neuronal response in the strychninized cortical suprasylvian gyrus was investigated in experiments on immobilized and unanesthetized cats using intracellular techniques. Paroxysmal depolarizing shifts (PDS) in neuronal membrane potential were recorded, consisting of a bursting discharge and slow depolarization wave. It was found when using intracortical stimulation that PDS can accumulate and change in shape and size. Bursting discharges in PDS were induced by large-scale EPSP which could be distinguished from paroxysmal response. Data from presumably intradendritic readings demonstrated the presence of large-scale EPSP during the generation of epileptiform discharges in the cortex. In a proportion of cells, PDS were accompanied by hyperpolarizing potentials — apparently IPSP, since they undergo reversal with intercellular administration of Cl^–. The contribution of excitatory and inhibitory synaptic influences to paroxysmal neuronal response is discussed.I. I. Mechnikov State University, Odessa. Translated from Neirofiologiya, Vol. 22, No. 5, pp. 642–649, September–October, 1990.     

Inhibition in the neurons of the somatosensory cortex and the possibility of intracortical propagation of excitation

Extra- and intracellular leads were used to study the reactions of neurons in the pyramidal tract (PT) of the cat brain to antidromic and afferent effects. It was shown that afferent activation of PT neurons proceeds heterogeneously. Three types of PT neurons were identified, successively involved in the impulse response to afferent stimulation. By means of paired stimuli we determined the heterogeneous changes in sensitivity of late reacting PT neurons. It was found that, under certain conditions, the different IPSP evoked by afferent stimulation or PT stimulation do not prevent the appearance of impulse responses to secondary synaptic activation. A conclusion was drawn from these experiments on the localization of the excitatory intracortical terminals on the somas of the PT neurons and on the limited effect of inhibitory processes upon intracortical propagation of the afferent signal reaching the cortex. A functional scheme of intracortical PT neuron links is presented.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the USSR, Kiev. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 465–473, September–October, 1971.