Dependence of EPSP summation pattern on membrane potential in mollusk neurons

The dependence of monosynaptic EPSP pattern on membrane potential level was investigated during experiments on identifiedPlanorbis corneus neurons. A random sequence of twin stimuli spaced at different intervals was used to ascertain this pattern. It was shown that the value of interstimulus interval corresponding to the most marked EPSP interactions mainly depended on postsynaptic mechanisms: selected changes in the parameters of the postsynaptic neuron leads to similar alteration in the summation function extremum. The possibility arises from these results of selective tuning (applying to each input or groups of inputs) to specific intervals (or frequencies); this tuning may be modulated according to changing membrane potential at the relevant portion of the neuron. The possible functional role of this mechanism is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 3, pp. 314–320, May–June, 1989.     

Response induced in prog motoneurons by glutamate application

It was shown during experiments on isolated frog brain (fromRana ridibunda) that response to microelectrophoretically injected glutamate on to various points on the somatodendritic motoneuronal membrane (GLU response) displayed the same properties as EPSP induced in the same motoneuron by activation of three different synaptic inputs. Techniques of transmembrane polarization and current chop by means of a single microelectrode were used in this research. Mean levels of reversal potentials of GLU response and EPSP occurring as a result of stimulating the reticular formation, dorsal root, and microstimulation of presynaptic elements at the point of glutamate application equaled –16.9 ± 1.7 (n=13), –6.8 ± 1.7 (n=13), –9.8 ± 1.8 (n=6), and –15.1 ± 1.4 mV (n=13), respectively. Summation of GLU response and EPSP were quasilinear. Changes (upwards) in conductance associated with GLU response did not exceed 10%. Findings would indicate that glutamate, acting on the postsynaptic membrane receptors, induces depolarization and may serve as transmitter in all three inputs investigated.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 6, pp. 776–785, November–December, 1988.     

Electrophysiological properties of neurons and neuronal organization of the crayfish somatogastric ganglion

Experiments with intracellular recording from neurons of the isolated crayfish somatogastric ganglion established that the membrane potential of the neurons is 53±3 mV. Single stimulation of the central branches of the ganglion evoked EPSP and a spike in the neurons. The spike amplitude was 7.5±0.6 mV. The small amplitude of the spike is explained by the fact that it arises at some distance from the body of the neuron and propagates electrotonically in it. Summation of several EPSP is necessary in most cases for initiation of the spike. When the orthodromic stimulus was strong enough, and IPSP occurred in some cells in addition to the EPSP and spike. Stimulation of the peripheral nerves of the ganglion induced in most neurons antidromic excitation and in some neurons orthodromic excitation. Some neurons spontaneously discharged rhythmically with an unstable frequency (11–27 impulses/sec). An investigation of the effect on neurons of chemical agents [acetylcholine, adrenalin, noradrenalin, gamma-aminobutyric acid (GABA), glutamic acid, and dopamine] showed that acetylcholine has the strongest and most stable depolarizing action and apparently is a synaptic transmitter in the ganglion. The other agents excited some neurons — depolarized them and evoked rhythmic discharges — and, coversely, hyperpolarized and suppressed the rhythmic activity of other neurons. A scheme of neuronal organization of the somatogastric ganglion of the crayfish is proposed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 3, pp. 307–313, May–June, 1970.     

Presynaptic mechanisms for intensifying reactivity of command neurons in Helix pomatia defensive behavior under the effects of vasopressin analog

This study set out to investigate presynaptic mechanisms underlying reactivity of command neurons inHelix pomatia defensive behavior under the effects of desglycine-arginine vasopressin, a vasopressin analog. Peptide perfusion was found to intensify accumulated EPSP in command neurons during stimulation of the nerve without affecting the monosynaptic connection between primary sensory and command neurons. It was concluded that parallel pathways exist for the spread of excitation from the periphery to command neurons. Properties of such pathways are described and neurons with similar properties are identified. It is in these same cells that long-term changes in spontaneous EPSP induced by application of the peptide were noted.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 6, pp. 723–730, November–December, 1990.     

Serotonin-induced changes in the action of functionally distinct neurons in Helix pomatia

The effects of serotonin on the amplitude of summated EPSP in interneurons and on the duration of action potentials in sensory neurons, interneurons, and motoneurons involved in avoidance behavior were investigated in functionally distinct neurons isolated from theHelix pomatia nervous system. The duration of action potentials in sensory neurons was found to increase under the effects of serotonin (and this could underly the rise in EPSP amplitude), although that of interneuron and motoneuron spikes did not change. The functional significance of selective neuronal response to a rise in serotonin concentration is discussed, together with the mechanics underlying such effects.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 316–322, May–June, 1987.     

Temporal summation in cat visual cortical neurons

Characteristics of temporal summation in neurons of area 17 of the visual cortex in acute experiments on unanesthetized, immobilized cats. During light adaptation, extracellular spike responses of these neurons to optimal local photic stimuli of varied duration — from 5 to 1000 msec — were studied. The critical duration of temporal summation of excitation, determined by the supraliminal method using the criterion of maximal discharge frequency in the first volley of the spike response, varied in different cells from 5 to 100 msec; neurons with summation lasting 15–100 msec (mean 31.45±5.67 msec) were found most frequently. Neurons with central receptive fields differed significantly from cellswith peripheral fields in the shorter critical duration of temporal summation, the lower frequency of spontaneous discharges, and the shorter duration of the first volley of the response. Summation time in neurons with simple receptive fields was significantly shorter than in neurons with complex receptive fields. The results of these experiments are compared with data in the literature obtained by the study of retinal and lateral geniculate neurons in cats and are discussed from the stand-point of division of ascending afferent projections in the visual system into X-and Y-groups (Ia and Ib).Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 4, pp. 345–352, July–August, 1981.     

Multiplicity of pacemaker zones in Helix pomatia neurons

Intracellular microelectrode recordings from neurons ofHelix pomatia revealed several local zones of action potential generation both on the soma and on some of the branches of the neurons. Under certain conditions the activity of individual loci of the neuron membrane was synchronized to produce a normal action potential. It is suggested that the somatic membrane of neurons is heterogeneous in structure and consists of separate loci of an electrically excitable membrane, incorporating active and latent pacemaker zones. Neurons ofH. pomatia are characterized by two types of action potential with different triggering mechanisms: one (synaptic) type is generated under the influence of the EPSP, the other (pacemaker) arises through activation of endogenous factors for the neuron (pacemaker potentials). The interaction between synaptic and pacemaker potentials during integrative activity of the neuron is discussed.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 5, No. 1, pp. 88–94, January–February, 1973.     

Peculiarities of summation processes in visual-sensitive neurons in the pretectal area of cat

Summation processes occurring in single neurons of the pretectal area in response to either moving or stationary light stimuli were studied in acute experiments on cats. In most neurons studied (85%), gradual increase of the angular size of stimulus resulted in clearly defined summation. In neurons lacking directional sensitivity (nondirectional neurons) the stimulus movement in two opposite directions caused, as a rule, similar and symmetrical changes in the number of spikes, whereas under the same conditions direction-sensitive neurons, in addition to symmetrical development of summation processes, could exhibit substantial differences in the summation curves. The responses to a preferred movement direction could be significantly inhibited or facilitated, while the responses to a non-preferred direction remained stable or changed reciprocally. Neuronal responses to different directions of the movement of stimulus might change independently of each other. This was also the case whenon andoff responses of theon—off neurons to stationary stimuli were compared. It is concluded that neurons of the pretectal area have a complex infrastructure of receptive fields that significantly influences the integration of incoming information.Neirofiziologiya/Neurophysiology, Vol. 25, No. 5, pp. 376–382, September–October, 1993.     

Direct cortical response in the cat motor cortex during summation

Summation was studied by a procedure close to that used in producing a conditioned reflex. Subthreshold electrical stimulation, which gave rise to a dominant focus in the cat motor cortex, was applied after photic stimulation. Under these conditions, summation occurred both when the two stimuli were applied simultaneously and when the weaker stimulus preceded the stronger one by a very short interval (tens of milliseconds). Increased excitability was characteristic of the dominant focus. An excessive increase in excitability weakened the summation reflex. Electrographically, this type of conditioning was reflected in an increase in amplitude of the primary negative wave of the direct cortical response, recorded in the motor area at a distance of 2–3 mm from the stimulation point. It is concluded from analysis of this electrophysiological phenomenon and comparison of the results with data in the literature that different mechanisms are involved in the summation process during different sequences of stimulation ("photic+electrical" and "electrical+photic").Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 1, No. 3, pp. 293–302, November–December, 1969.     

Unit responses in the auditory cortex to stimulation of geniculocortical fibers

Extracellular and intracellular single unit responses of neurons of the auditory cortex to electrical stimulation of geniculocortical fibers (GCF) were recorded in experiments on cats immobilized with tubocurarine. The latent period of responses of 15% of neurons to GCF stimulation was 0.3–1.5 msec. It is postulated that they were excited anti-dromically. The latent period of spikes generated by neurons responding to GCF stimulation orthodromically varied from 1.6 to 12 msec. In 28.6% of neurons the latent period was 1.6–2.5 msec. It is postulated that these neurons were excited monosynaptically. Intracellular recording revealed primary IPSPs in response to GCF stimulation in 63.3% of neurons, a brief EPSP followed by a prolonged IPSP in 17.7%, an EPSP-spike-IPSP complex in 12.3%, and subthreshold EPSPs in 7% of neurons. The latent period of the primary IPSPs varied from 1.8 to 11 msec, being 1.8–3.7 in 72%, 3.8–5.7 in 20.0%, and 5.8–11 msec in 8.0% of neurons. The latent period of responses beginning with an EPSP was 1–4 msec (mean 1.8 msec). Orthodromic responses arising 3–10 msec after the antidromic response, and consisting of 3–5 spikes, were recorded in some antidromically excited neurons. Hypotheses regarding the functional organization of the auditory cortex and mechanisms of inhibition in its neurons are put forward on the basis of the results obtained.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 227–235, May–June, 1972.     

Electric reactions of the auditory cortex areas in bats to ultrasonic stimuli with various fill frequencies

The overall electric reactions and action potentials of single neurons in the auditory cortex were investigated for Vespertilionidae (Myotis oxygnathus) and Rhinolophidae (Rhinolophus ferrum equinum) narcotized with Hexenal. In the Vespertilionidae the greatest sensitivity to ultrasound is manifest at frequencies from 10 to 50 kHz, and in the Rhinolophidae for the ranges from 10 to 40 and from 82 to 84 kHz. The shapes of the response areas of single neurons in both types of bats are similar except for neurons discovered in Rhinolophidae that have three response areas with characteristic frequencies in the ranges 27–28, 40–42, and 80–84kHz. Narrow response areas with characteristic frequencies in the range from 70 to 90kHz appear on a considerable proportion of the neurons in the Rhinolophidae, but not the Vespertilionidae. Low thresholds are recorded to the stimulus cutoff in the range from 76 to 86 kHz.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 526–532, September–October, 1971.     

Reversal potential for monosynaptic EPSP in frog motoneurons

Experiments were conducted on brain isolated from the frogRana ridibunda using a current chop technique of transmembrane polarization and discrete measurement of membrane potential by a single microelectrode during intervals between waves of current. It was found that the current-voltage relationship of the motorneuron is non-linear; i.e., membrane resistance decreases considerably in step with increased depolarizing current. After the initial reduction, membrane resistance began to climb back when a more protracted current lasting 1–2 min was applied; consequently membrane potential level shifted towards more positive values of +50 mV and above at current levels of 40–60 nA. It then became possible to bring about complete reversal of monosynaptic EPSP produced in the lumbar motoneurons by stimulation of the brainstem reticular formation or by microelectrode stimulation of the ventrolateral tract descending fibers and to measure reversal potential of these EPSP directly, without resorting to computing or extrapolation. Measurements varied mainly between 0 and –10 mV.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 534–542, 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.     

Characteristics of electrical responses by the medial geniculate bodies in Vespertilionidae and Rhinolophidae to ultrasonic stimuli with different frequencies

The total electrical responses and action potentials of the neurons in the medial geniculate bodies in Vespertilionidae and Rhinolophidae were investigated. Maximum sensitivity to ultrasonic stimuli was recorded inMyotis oxygnathus (Vespertilionidae) in the range 10–40 kc/sec and 65–80 kc/sec, and in Rhinolophidae in the ranges 10–70 kc/sec and 81–86 kc/sec. Low thresholds were observed inMyotis oxygnathus for the frequencies covered by their echo-location cries, whereas the thresholds recorded in Rhinolophidae in the 80 kc/sec band (the principal frequency of their echo location cries) were 15–30 dB higher than those for adjacent frequencies. Minimum thresholds of off-responses were observed inMyotis oxygnathus in the range 50–60 kc/sec, and in Rhinolophidae in the range 78–80 kc/sec. The regions of neuronal response in both species of bat were generally similar in form to those of responses recorded in the medial geniculate bodies of other mammals. Some of the neurons in Rhinolophidae with a characteristic frequency of about 80 kc/sec were also sensitive to stimuli with one-half and one-third of the principal frequency. In Rhinolophidae the greatest selectivity for frequencies was possessed by neurons that responded within the range from 80 to 90 kc/sec.A. A. Zhadanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 138–144, March–April, 1971.     

Role of cortical inhibition in heterosensory interaction of neurons of the cat sensorimotor cortex

Background and evoked neuronal activity in the cat sensorimotor cortex was recorded under a-chloralose anesthesia. Pairs of heterogeneous stimuli were applied, spaced at intervals of 0, 100, 200, 300, and 400 msec. A clicking sound, flashing light, and electroshock to the contralateral forepaw were used as stimuli. Partial or complete blockade of response to test stimuli presentations spaced 100–200 msec apart were observed when using stimulation of varying modality. The greatest test response was recorded at interstimulus intervals of 200–300 msec. Intracellular mechanisms of heterosensory interaction were investigated by applying the inhibitory transmitter antagonist picrotoxin microiontophoretically to the test cell to produce local attenuation of inhibitory effects. This substance also reduced the duration of blockage following the conditioning stimulus and the occurrence of peak level test response at a lower interstimulus interval than in the controls. Either a consistent increase in the number of spikes per response at one of the interstimulus intervals or a uniform reinforcement in unit response to several different interstimulus intervals were observed in a proportion of the cells. The contribution of intracortical inhibitory influences to the mechanisms of heterosensory interaction on neurons of the cat sensorimotor cortex is discussed in the light of our findings.A. A. Ukhtomskii Institute of Physiology, A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 147–156, March–April, 1987.     

Ionic mechanisms of excitatory action of transmitter,exogenous acetylcholine,and serotonin on superior cervical ganglion neurons in rabbits

Ionic mechanisms of EPSP generation and depolarization induced by iontophoretic application of acetylcholine (ACh) and serotonin (5-hydroxytryptamine, 5-HT) — acetylcholine and serotonin potentials — were investigated in neurons of the isolated rabbit superior cervical ganglion by means of intracellular microelectrodes. The reversal potentials (E_r) for EPSP and the ACh-potential were –14.4±1.6 and –16.5±1.2 mV respectively, and they were about the same for the 5-HT potential. In some neurons (about one-third) much more negative values for E_r were obtained for EPSP and the ACh-potential by extrapolation, probably due to an increase in the resistance of their membrane during hyperpolarization. A decrease in the external sodium and potassium concentrations was shown to make E_r for EPSP and the ACh-potential more negative, whereas an increase in the external potassium concentration made it more positive than in normal solution; a change in the external chloride concentration did not alter E_r. It is suggested that the excitatory transmitter and exogenous ACh (and also, probably, 5-HT) share the same ionic mechanism of action of the membrane, which includes an increase in the permeability of the membrane to two ions — sodium and potassium — simultaneously.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 6, pp. 637–644, November–December, 1978.     

Single unit responses in the auditory center of the frog mesencephalon to amplitude-modulated tones

Responses of most single neurons of the torus semicircularis ofRana ridibunda to stimuli of characteristic frequency and with low (10–30%) sinusoidal amplitude modulation were considerably stronger than those of the same neurons to pure tones. Analysis of phase histograms synchronized with the period of modulation was used to study dependence of the response on the frequency of modulation. In some cells the degree of modulation of the phase histogram fell steadily with an increase in modulation frequency, but in others a maximum was found in the 10–20 Hz region. Usually modulations of the phase histogram were significantly greater than stimulus modulation. The phase angle between the maximum of stimulus amplitude and the maximum of the unit response increased as an approximately linear function of the increase in modulation frequency.N. N. Andreev Acoustic Institute, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 3, pp. 264–271, May–June, 1980.     

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.     

Effects of applying oxytocin to Helix pomatia neurons. II. Hyperpolarization

The ionic mechanisms of hyperpolarization produced by applying oxytocin (OT) were investigated at the membrane of identifiedHelix pomatia neurons. Two types of neuron were known to exist, in one of which hyperpolarization is produced by a reduction in chloride ions at the membrane and a rise in membrane permeability to potassium ions in the other. In the first of these, response to OT had a reversal potential of –40 mV and decreased when furosemide and tolbutamide were added to the external medium. In the second case, the potential of the reversal of the response to OT was –70 mV. Upon doubling of potassium ion concentration in the external solution it was shifted towards depolarization by 15 mV. It is sugested thatHelix pomatia neurons have different types of OT receptors, some of which, when activated, manifest reduced chloride permeability at the membrane (probably through the cell cyclase system) with a rise in potassium permeability at the membrane in others.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 5, pp. 659–666, September–October, 1988.     

Electrophysiological investigation of central neurons of the electroreceptor system of the skate

Bioelectrical responses of acoustico-lateral neurons to electrical stimulation of the ampullae of Lorenzini were investigated in acute experiments on the anesthetized Black Sea skateTrigon pastinaca. Three types of responses were found: a primary composite response, prolonged activity, and single unit activity. Excitation of the neurons corresponded to a more marked negative phase, and inhibition to a more marked positive phase of the primary response. The thresholds of the unit responses to adequate electrical stimulation were 10^–9–10^–10 A/mm² and the minimal latent period 20 msec. The spontaneous activity of some neurons clearly depended on the animal's respiration. The character of the response depended on stimulus polarity, as reflected in the appearance of on- and off-responses. A tonic type of response with features of adaptation was predominant. The dependence of some response parameters (latent period of on- and off-responses, firing rate, duration of the contrast interval, response thresholds) on those of the stimulus is analyzed. The mechanisms of these bioelectrical responses are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol.6, No.1, pp.59–67, January–February, 1974.