Origin of orthodromic evoked potential in the frog olfactory bulb

The functional organization of the primary olfactory center of the frog was investigated. The dynamics of changes in individual components of the potential evoked by electrical stimulation of the olfactory nerve corresponds to morphological evidence of the asymmetrical structure of the frog olfactory bulb. The character of spatial localization and of the properties of individual components of the orthodromically evoked potential suggests that a monosynaptic reciprocal activating system participates in the production of the main component of the response. The similarity between the durations of the inhibitory pauses in spontaneous activity of the mitral cells during stimulation of the olfactory nerves and of the lateral olfactory tract indicates that when all these methods of stimulation are used a single system controlling excitability of the secondary neurons is activated. It is postulated that inhibition of the mitral cells is evoked as a result of activation of a polysynaptic recurrent system incorporating interneurons.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 184–191, March–April, 1972.     

Analysis of long-latency components of field potentials evoked by stimulation of the cerebral cortex and nerves in the cerebellar paramedian lobule

Field potentials evoked in the graunular layer of the cerebellar paramedian lobule of unanesthetized cats in response to stimulation of the sensomotor cortex and limb nerves contained slow negative waves, appearing after a long latent period, which were generated by granule cells. In the case of nerve stimulation this component was recorded both inside and outside the projection zone of the corresponding limb. Cortical stimulation by single stimuli or series of stimuli not more than 1.8–2.5 times above threshold strength led to the appearance of evoked potentials only inside the corresponding projection zone. The long-latency component of field potentials evoked by cerebral stimulation followed high frequencies of repetitive stimulation and was less sensitive to the action of barbital anesthesia than the analogous component of potentials evoked by nerve stimulation. In the case of combined cerebral and nerve stimulation the long-latency components underwent summation. It is concluded that mossy fibers of slowly-conducting spino- and cerebrocerebellar tracts innervate different granule cells in the cerebellar cortex.Institute of Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 379–385, July–August, 1982.     

The source of spontaneous activity in the main olfactory bulb of the rat

Introduction

In vivo, most neurons in the main olfactory bulb exhibit robust spontaneous activity. This paper tests the hypothesis that spontaneous activity in olfactory receptor neurons drives much of the spontaneous activity in mitral and tufted cells via excitatory synapses.

Methods

Single units were recorded in vivo from the main olfactory bulb of a rat before, during, and after application of lidocaine to the olfactory nerve. The effect of lidocaine on the conduction of action potentials from the olfactory epithelium to the olfactory bulb was assessed by electrically stimulating the olfactory nerve rostral to the application site and monitoring the field potential evoked in the bulb.

Results

Lidocaine caused a significant decrease in the amplitude of the olfactory nerve evoked field potential that was recorded in the olfactory bulb. By contrast, the lidocaine block did not significantly alter the spontaneous activity of single units in the bulb, nor did it alter the field potential evoked by electrical stimulation of the lateral olfactory tract. Lidocaine block also did not change the temporal patters of action potential or their synchronization with respiration.

Conclusions

Spontaneous activity in neurons of the main olfactory bulb is not driven mainly by activity in olfactory receptor neurons despite the extensive convergence onto mitral and tufted cells. These results suggest that spontaneous activity of mitral and tufted is either an inherent property of these cells or is driven by centrifugal inputs to the bulb.     

Sensory interaction in the snailHelix lucorum

The activity of hair cells of statocysts inHelix lucorum was investigated by means of intra- and extracellular recording, applying appropriate stimulation of the organs of balance, optic photoreceptors, and the chemoreceptors of the optic tentacle bulb. Mechanical stimulation of the statocysts evoked a firing reaction in the hair cells as a result of generator potentials occurring at the receptors. The amplitude of generator potentials was proportional to the intensity of the reaction. Stimulating the optic photoreceptors by switching on a light produced a spike response in the hair cells with a short latency of 0.3–2 sec. The latent period of this response was inversely proportional to the intensity of the light. Appropriate stimulation of the chemoreceptors of the optic tentacle bulb caused a faint spike response with a long latent period of 20–40 sec in the hair cells. Illumination and stimulation of the chemoreceptors produced an inhibitory response in the form of bursts of IPSP in 2 out of more than 50 hair cells.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 17–26, January–February, 1986.     

Investigation of the mechanism of temperature sensitivity of the electroreceptors of ampullae of lorenzini

In experiments on Black Sea skates (Raja clavata), the potential of the receptor epithelium of the ampullae of Lorenzini and spike activity of single nerve fibers connected to them were investigated during electrical and temperature stimulation. Usually the potential within the canal was between 0 and –2 mV, and the input resistance of the ampulla 250–400 k. Heating of the region of the receptor epithelium was accompanied by a negative wave of potential, an increase in input resistance, and inhibition of spike activity. With worsening of the animal's condition the transepithelial potential became positive (up to +10 mV) but the input resistance of the ampulla during stimulation with a positive current was nonlinear in some cases: a regenerative spike of positive polarity appeared in the channel. During heating, the spike response was sometimes reversed in sign. It is suggested that fluctuations of the transepithelial potential and spike responses to temperature stimulation reflect changes in the potential difference on the basal membrane of the receptor cells, which is described by a relationship of the Nernst's or Goldman's equation type.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov, Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Pacific Institute of Oceanology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 67–74, January–February, 1980.     

Centrifugal effects on amacrine cells in the frog's retina

The effect of electrical stimulation of the optic nerve on various cells in the frog's retina was investigated by two methods: by the histochemical method (measurement of the amount of RNA in separate cells), and by intracellular recording of potentials. Rhythmic (5 per sec) stimulation of the nerve induced an increase in the amount of RNA in ganglion cells, and especially in amacrine cells. The level of RNA in bipolar and horizontal cells did not change. The results of the experiment indicate that in frogs (as in birds) centrifugal effects are produced through amacrine cells. In electrophysiological experiments reactions to stimulation of the nerve were manifested only in ganglion and amacrine cells. In the ganglion cells that was an antidromic impulse, but sometimes also a delayed impulse, which was evidently the result of secondary excitation of the cell. In amacrine cells the response consisted of a short excitant postsynaptic potential with a discharge of impulses superimposed on it. Data are presented indicating the existence of amacrine cells of different types, probably fulfilling different functions.Institute of Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 3, pp. 293–300, May–June, 1971.     

Posttetanic changes in hippocampal minimal evoked potentials

Changes in the EEG induced by a single spike were recorded in the hippocampus of an unanesthetized rabbit. Summation of focal electrical activity synchronous with spontaneous single unit discharges at the symmetrical point of contralateral hemisphere revealed no stable potentials which could reflect these changes. In two cases discharges identified as activity of Shaffer's collaterals were recorded in area CA₁. Summation of post-spike changes in evoked activity recorded by the same microelectrode showed stable negative waves with an amplitute of 40–60 µV, which could have been evoked by single spikes. The curve of amplitude of the averaged evoked potentials versus near-threshold current strength stimulating the intrahippocampal pathways was not smooth in most experiments but stepwise in character. It is suggested that the minimal evoked potential corresponding to the first step (amplitude 40–80 µV) reflects a response to stimulation of one fiber. After above-threshold tetanization prolonged posttetanic potentiation of the minimal evoked potentials did not arise in CA₁ in response to stimulation of Shaffer's collaterals. Minimal evoked potentials recorded in area CA₃ in response to stimulation of the dentate fascia showed clear potentiation. The results are in agreement with the hypothesis of the synaptic localization of the mechanisms responsible for prolonged posttetanic potentiation.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 2, pp. 124–134, March–April, 1977.     

Formation of functional synaptic connections between heterogeneous brain formations in organotypic nerve tissue culture

The principles of oriented growth of nerve fibers and the formation of functional synaptic connections during combined culture of brain structures with no direct anatomical or functional connections (the spinal cord and olfactory bulbs of mouse embryos) were investigated by neuromorphological and electrophysiological methods. During the first week of culture connections, mainly glio-neuronal bridges, formed between the explants of spinal cord and olfactory bulb. Glial cells forming an oriented substrate, facilitating growth and fasciculation (the formation of bundles) of axons that developed subsequently, play an active role in the formation of such connections. In preparations impregnated with silver, connections formed by bundles of axons or by single nerve fibers were seen between the explants. The results of electrophysiological investigations of combined cultures of heterogeneous brain structures showed that by the second week of culture functional synaptic connections have formed between explants of spinal cord and olfactory bulbs. Electrical stimulation of spinal cord explants led to the appearance of short- and long-latency unit responses in explants of the olfactory bulbs. The formation of nonspecific functional synaptic connections for these brain structures during combined culture, revealed by this investigation, is evidence of the high level of morphogenetic plasticity of growing or regenerating axons and of the active role of neuroglial cells in preparation and provision for oriented growth of nerve fibers.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 490–497, September–October, 1980.     

Changes in electrical activity of spinal cord neurons in adrenalectomized rats under the effects of corticosteroid hormones

The effects of glucocorticoid (dexamethasone) and mineralocorticoid (deoxycorticosterone) hormones on electrical excitability of nerve cells belonging to the dorsal and ventral horns of the spinal cord induced by stimulating the sciatic nerve, as well as background and evoked activity in single dorsal horn cells were investigated during experiments on adrenalectomized spinal rats using intracellular techniques for recording potential. Both hormones were found to produce mainly facilitatory effects in adrenalectomized animals, manifesting in increased background activity rates in single cells and higher amplitude of field potentials in nerve cells of the dorsal half of the spinal cord. It was shown that neuronal response followed different patterns in the ventral half of the spinal cord gray matter under the action of gluco- and mineralocorticoids: dexamethasone and deoxycorticosterone respectively increased and reduced the amplitude of field potentials in the motoneuronal region. Findings indicate the modulatory influence of adrenal cortical hormones on the electrical activity of spinal cord neurons.Institute of Experimental Biology, Academy of Sciences of the Armenian SSR, Erevan. I. A. Orbeli Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 233–238, March–April, 1989.     

Functional development of hippocampal mossy fiber synapses in rabbits

The course of functional maturation with age of mossy fiber synapses on pyramidal cells in areas CA_3,4 of the dorsal hippocampus was investigated by extracellular recording of focal potentials and single unit responses of the hippocampus to electrical stimulation of the dentate fascia in waking, unimmobilized rabbits aged from 1 to 14 days. After the 4th day of postnatal life focal potentials appeared in response to single stimulation, in the form of a biphasic short-latency wave, characteristic of responses of the mature hippocampus, accompanied by spike discharges with a latent period of 3 to 10 msec and inhibitory responses of the hippocampal neurons. During the next 10 days the amplitude of the focal potentials increased from several hundred millivolts, with the sharpest increase observed from the 4th through the 7th days. In early age periods global and unitary responses were shown to be capable of frequency potentiation and also of short-term after-potentiation.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 3, pp. 246–254, May–June, 1980.     

Excitability of the sensomotor cortex and red nucleus of rabbits at different levels of spatial synchronization of cortical potentials

To determine the excitability of the rabbit sensomotor cortex and red nucleus the animal's motor response to electrical stimulation of these structures at threshold strength was investigated. In computerized experiments the excitability of these structures was compared in situations characterized by different degrees of correlation of cortical potentials. An increase in the level of spatial synchronization of cortical potentials was shown to be accompanied by an increase in the excitability of the sensomotor cortex and red nucleus. This increase in excitability is evidently a neurophysiological mechanism of the increase in probability of appearance of an effector response to sensory stimulation when the level of spatial synchronization of cortical potentials is raised.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 19–24, January–February, 1977.     

Effect of noradrenalin and serotonin on responses of area CA3 neurons evoked in guinea pig hippocampal slices by electrical stimulation of mossy fibers

The effect of noradrenalin (NA) and serotonin (5-HT) on responses of area CA₃ cells evoked by electrical stimulation of mossy fibers was studied in slices of guinea pig hippocampus survivingin vitro. Both substances, which modify the general level and organization of spontaneous activity, also affected responses of area CA₃ cells. Changes in magnitude and structure of the response usually correlated with corresponding changes in spontaneous activity. In certain cases NA, which lowered the frequency of spontaneous activity but increased its relative content of "complex discharges" and also the number of reduced action potentials in the complex discharge, also led to an increase in the response to stimulation. 5-HT evoked periodic grouped activity in some cells and led to the appearance of such grouped discharges for the first time in the responses of other cells. Unlike NA, 5-HT caused prolonged (up to 40 min) after-facilitation of the response and an increase in spontaneous discharge frequency.Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 410–417, July–August, 1982.     

Frequency characteristics of skate electroreceptive central neurons responding to electrical and magnetic stimulation

Responses of single neurons in the lateral lobes of the medulla to stimulation of the electroreceptive system by homogeneous sinusoidal electrical and magnetic fields were investigated in acute experiments on the skateRaja radiata. Thresholds of neuronal responses to electrical stimulation varied from 0.03 to 10 µV/cm. The optimal frequency ranges for electrical and magnetic reception were in the regions of 0.05–5 and 2–3 Hz respectively. The possible mechanisms and functional significance of frequency characteristics of central neurons are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. All-Union Cardiologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 464–470, July–August, 1984.     

Influence of lithium ions on the electrical activity of nerve cells of the leech

The influence of lithium ions on the electrical activity of the nerve cells of the leech,Hirudo medicinalis, was investigated by the method of microelectrode recording. It was discovered that the electrical activity of the giant nerve cells disappears rapidly in a solution with lithium ions. In such a solution, the membrane of these cells is depolarized by 5–7 mV; however, polarization of the cells with direct current does not lead to a restoration of their activity. Possible mechanisms of the inability of lithium ions to replace sodium ions in the generation of the action potentials of leech nerve cells are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 2, No. 6, pp. 636–642, November–December, 1970.     

Differences in human evoked potentials related to olfactory or trigeminal chemosensory activation

The aim of the present study was to determine, whether there are differences in the topographical distribution of chemosensory evoked potentials (CSEPs) due to stimulation with different odous substances. The odorants used in the study which mainly excited the olfactory nerve were vanillin and acetaldehyde; those which additionally excited the trigeminal nerve were sulphur dioxide and ammonia. Twelve subjects participated in the study. The subjects separately estimated the intensity of the odorous and of the painful/pricking sensation caused by the stimuli, and described the odorous qualities in their own words. CSEPs were recorded from 7 positions.After stimulation with “olfactory” subsances maximum CSEP amplitudes were recorded at parietol-central sites, and after stimulation with “trigeminal” substances maximum amplitudes were obtained at the vertex. Following stimulation with ammonia and sulphur dioxide amplitudes were largest contralateral to the stimulated nostril. In contrast, little difference in CSEP amplitudes was observed between hemispheres after stimulation with vanillin or acetyldehyde.Thus, the topographical distribution of CSEP amplitudes may provide information with regard to the sensory system (olfactory or trigeminal) activated by the presentation of an odorous stimulus.     

Effect of background illumination on evoked potentials of the visual system in the turtle

We discovered an enhancing effect of background illumination on amplitude and total duration of electrical reactions of the tectum of the midbrain and pallial thickening in response to a flash and electrical stimulation of the optic nerve. This effect is analogous to the phenomenon of photic potentiation known for the visual system of mammals. Changes of evoked potentials in the contralateral pallial thickening and tectum were fairly stable and survived throughout the course of the entire period of illumination (up to 30 min). The effect was intensified with an increase of illumination intensity. Intensification of response on the part of the tectum and pallial thickening during steady illumination was accompanied by a weakening of slow background electrical activity. During the action of background illumination, the excitability of the tectum rose considerably with direct electrical stimulation. The influence of prolonged illumination on responses of the tectum and pallial thickening was more clearly detected at submaximal strengths of stimulation of the optic nerve or tectum. All of the effects of photic potentiation are confined to centers contralateral to the illuminated eye. This indicates the absence of diffuse effects on excitability of the turtle brain.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 1, No. 2, pp. 219–224, September–October, 1969.     

Effects of transcranial electrical stimulation of opioid brain structures on regeneration of peripheral nerves in the rat

The effects of transcranial electrical stimulation of opioid brain structures on regeneration of the rat sciatic nerve after transection and microsurgical suturing of the nerve were investigated. Electrical stimulation was found to accelerate regeneration of motor and sensory fibers of the sciatic nerve. The subject of the involvement of endogenous opioid peptides in regeneration of the peripheral nerves is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 76–79, January–February, 1990.     

Unit responses of the cerebellar cortex to stimulation of the vagus nerve and nerves of the limbs

Responses of 74 cerebellar cortical neurons to electrical stimulation of the vagus nerve and its gastric branches and also of the limb nerves were recorded extracellularly in experiments on rats anesthetized with chloralose and pentobarbital. Phasic and tonic unit responses were similar to all types of stimulation, but fewer neurons responded to stimulation of the vagus nerve than to stimulation of the limb nerves. Monosensory neurons responding only to visceral stimulation, were not found. Among cells giving a phasic response, some had a short and others a long latent period. The latent period of responses of all types was longer to vagal stimulation than to stimulation of the limb nerves. The maximal frequency of rhythmic responses to vagal stimulation was 8/sec, compared with 16/sec for stimulation of the limb nerves. Tonic responses of the neurons were excitatory, inhibitory, and mixed. The type of unit response could vary depending on the frequency and repetitiveness of the stimuli but was otherwise independent of the type of stimulation.N. I. Pirogov Vinnitsa Medical Institute. I. M. Sechenov Institute of Evolutionary Biochemistry and Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 5, pp. 471–479, September–October, 1972.     

Changes in distribution of synaptic vesicles in endings of cones during electrical stimulation of the retina

Conditions (hypoxia) were chosen under which, judging from the reduction in the responses of the horizontal cells to electrical stimulation of the retina, mediator is exhausted in the presynaptic endings of the photoreceptors. Under these circumstances a number of "small" synaptic vesicles were shown to be reduced in those parts of the cones which are in direct contact with presynaptic membranes. No significant changes were found in the total number of "small" vesicles in the cone endings.Institute for Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 620–623, November–December, 1976.     

Role of calcium ions in response generation by the scallop abdominal sensory organ

The effect of calcium-free solution, cadmium ions, and theophylline on the global spike response in a nerve arising from the abdominal sensory organ of the scallopPatinopecten yessocensis, evoked by mechanical stimulation of that organ, was investigated. Removal of Ca ions from the external medium and addition of 10 mM CdCl₂ to it were shown to reversibly inhibit the combined spike response. Addition of theophylline to the external medium in a concentration of 5 mM caused an increase in amplitude of the spike response. These results indicate that Ca ions play a direct part in transformation of the mechanical stimulus into an electrical signal, and also that this process may be regulated by intracellular cAMP-dependent reactions.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Pacific Oceanologic Institute, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 475–480, July–August, 1984.