Distribution of myelinated and nonmyelinated nerve fibers of a cat cutaneous nerve in the spinal roots

The distribution of myelinated and nonmyelinated nerve fibers of the saphenous nerve of cats in the ventral and dorsal roots of the spinal cord was investigated by methods improving the signal—noise ratio in records of evoked responses from the nerve. The fibers of this nerve enter the spinal cord through roots of segments L_4–6. Nerve fibers with conduction velocities of between 80 and 0.38 m/sec were distributed in the dorsal roots of these segments. Four groups of nerve fibers with conduction velocities of 80–60, 40–30, 12.0–3.0, and 1.1–0.51 m/sec, possibly afferent in nature, were found in the ventral roots. The conditions of origin and detection of low-amplitude potentials in the roots of the spinal cord and the probable functional role of the nerve fibers in the ventral roots are discussed.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii State University, Gor'kii. Translated from Neirofiziologiya, Vol. 7, No. 6, pp. 647–654, November–December, 1975.     

Loss and recovery of the blood–nerve barrier in the rat sciatic nerve after crush injury are associated with expression of intercellular junctional proteins

The blood–nerve barrier in peripheral nerves is important for maintaining the environment for axons. Breakdown of the barrier by nerve injury causes various pathologies. We hypothesized that the breakdown and recovery of the blood–nerve barrier after injury are associated with the changes in the expression of intercellular junctional proteins. To test this hypothesis, we induced crush injuries in the rat sciatic nerve by ligation and analyzed spatiotemporal changes of claudin-1, claudin-5, occludin, VE-cadherin, and connexin43 by immunoconfocal microscopy and morphometry and compared them with changes in the permeability of the blood–nerve barrier by intravenous and local administration of Evans blue–albumin (EBA). On day 1 after removal of the ligature EBA leaked into the connective tissue in the endoneurium and then the leakage gradually decreased and disappeared on day 7. On day 1 claudin-1, claudin-5, occludin, VE-cadherin, and connexin43 had totally disappeared from the perineurium and endoneurium. Thereafter, claudin-1, claudin-5, occludin, and VE-cadherin recovered from day 2, whereas connexin43 was redetected on day 5. These results indicate that the breakdown and following recovery of the blood–nerve barrier are closely associated with changes in the expression of claudins, occludin, VE-cadherin, and connexin43 and that the recovery time course is similar but nonidentical.     

Influence of opioid peptides on nerve tissue in vitro

The influence of opioid peptides (gamma- and beta-endorphins, leu- and met-enkephalins, as well as certain synthetic analogs of enkephalin) was investigated on organotypic cultures of rat spinal and sympathetic ganglia. The cellular composition and size of the zone of growth were evaluated on the basis of intravital observations and an analysis of the specimen obtained using the method of impregnation, according to Holmes and the detection of catecholamines with glyoxylic acid. It was established that under the action of all the investigated substances that possess high affinity for opiate receptors, growth of the neurites from an explant was enhanced, and the number of glial and fibroblastoid cells in the growth zone was increased. The effect was observed most distinctly on a model of sympathetic ganglia. The tested compounds exhibited a significant growth-stimulating effect in the range of concentrations 10^–8–10^–14 M. The maximum size of the growth zone of the explants of the sympathetic ganglia in the case of a mean effective concentration of the peptides 10^–10 M by the third to fifth day of culturing was approximately 2–2.5 times this value in the control. The reaction was similar to the response of the nerve cells to nerve growth factor, used as a standard. Thus, the opioid peptides exhibit a pronounced growth effect on the structures of the nerve tissue under conditions of culture. It is suggested that this group of compounds, together with its currently well-known functions, may play a definite role in processes of the development and regenera-of nerve tissue.Institute of Experimental Cardiology, All-Union Cardiologic Science Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 550–557, July–August, 1985.     

EPSPs of masseter motoneurons evoked by stimulation of low-threshold infraorbital nerve afferents in cat

Stimulation of the infraorbital nerve at strengths 1.4–2.5 times higer than the threshold of excitation of A fibers in cats anesthetized with chloralose and pentobarbital evoked EPSPs with an amplitude up to 3.0 mV and a duration of 9–15 msec in 69% of masseter motoneurons after 1.5–3.0 msec. These EPSPs were complex and formed by summation of simpler short-latency and long-latency EPSPs. The short-latency EPSPs appeared in response to infraorbital nerve stimulation at 1.1–1.5 thresholds and had a slow rate of rise (2.5–4.5 msec, mean 3.7±0.4 msec), low amplitude (under 2.0 mV), and short duration (5–6 msec). Their latent period varied from 1.5 to 3.0 msec (mean 2.1±0.2 msec). The shortness of the latent period and its constancy during stimulation of the nerve at increasing strength, and also the character of development of facilitation and inhibition of the EPSP during high-frequency stimulation suggests that these EPSPs are monosynaptic. The slow rate of rise suggested that these EPSPs arise on distal dendrites of the motoneurons. Long-latency EPSPs appeared 7–9 msec after stimulation of the infraorbital nerve at 1.1–1.5 thresholds. Their amplitude reached 1.5–2.0 mV and their duration 7–9 msec. The long duration of the latent period combined with low ability to reproduce high-frequency stimulation (up to 30/sec) points to the polysynaptic origin of these EPSPs.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 583–591, November–December, 1977.     

An X-ray study of the pH property of frog sciatic nerve

Low-angle X-ray diffraction patterns have been recorded from frog sciatic nerve in pH solutions of 0.1–13.0. The normal X-ray pattern of frog sciatic nerve in Ringer's solution is maintained at pH 4.0–10.0. In acid pH, 2.5–4.0, and in alkaline pH, 10.0–11.0, the nerve myelin is in the partial swollen state. The partial swollen state and the normal state are reversible. Two physical states, the anomalous swollen state and the condensed state, at acid pH below 2.5 and the separated state at alkaline pH above 12.3 have been identified. These three physical states, the anomalous swollen state, the condensed state and the separated state, are reversible with each other on changing the pH solution but the normal state cannot be regained.     

The neurohypophysis of the crested newt

Summary In the median eminence of the newt a medial region and two lateral regions are described.In cross section, the medial region appears to be made up of 1) an outer or glandular zone (Zone I) containing aldehyde-thionine-positive and negative nerve fibres and blood capillaries. Nerve fibres appear aligned in palisade array along the capillaries. 2) An inner zone (Zone II) made up of a) a layer of aldehyde-thionine-positive nerve fibres (fibrous layer) belonging to the preoptic hypophyseal tract and b) a layer of ependymal cells lining the infundibular lumen and reaching the blood vessels with their long processes.The lateral regions display a less pronounced stratification and aldehyde-thionine positive nerve fibres are nearly absent.A slender lamina (ependymal border) containing mainly aldehyde-thionine-positive nerve fibres and ependymal cells connects the median eminence to the pars nervosa.At the ultrastructural level, in the outer zone of the medial region at least 4 types of nerve fibres and nerve endings are identified:Type I nerve fibres containing granular vesicles of 700–1000 Å and clear vesicles (250–400 Å).Type II nerve fibres containing granular vesicles and polymorphous granules of 900–1300 Å and clear vesicles (250–400 Å).Type III nerve fibres containing dense granules of 1200–2000 Å and clear vesicles of 250–400 Å.Type IV nerve fibres containing only clear vesicles of 250–400 Å. In the inner zone too, all these nerve fiber types are found among ependymal cells, while the fibrous layer consists of nerve fibres containing granules of 1200–2000 Å in diameter.In the lateral regions Type I, Type II and Type IV nerve fibres and their respective perivascular terminals are found; axons containing dense granules (1200–2000 Å) are scanty. In these regions typical synapses between Type I nerve fibres and processes rich in microtubules are visible.The classification and functional significance of nerve fibres in the median eminence are still unsolved, but it may be assumed that nerve fibres of the medial region belong to both the preoptic hypophyseal and tubero hypophyseal tract, while the lateral regions are characterized by nerve fibres of the tubero hypophyseal tract. Peculiar specializations of the ependymal cells in the median eminence of the newt are also discussed.Work supported by a grant from the Consiglio Nazionale delle Ricerche.The authors are indebted to Mr. G. Gendusa and P. Balbi for technical assistance.     

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.     

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.     

Electron-microscopic analysis of adrenergic nerve endings in the cat caudal mesenteric ganglion

The ultrastructure of nerve endings of the cat caudal mesenteric ganglion was studied after fixation of the material with 4% lithium permanganate solution by Richardson's method in the modification of Hökfelt et al. [12]. This fixation method was shown to permit the demonstration of numerous adrenergic as well as cholinergic nerve endings. Four types of adrenergic organelles were distinguished in neurons of the ganglion: small and large granular vesicles 30–50 and 70–90 nm in diameter, respectively, a tubular reticulum with electron-dense contents, and small granular vesicles 15–20 nm in diameter. The localization of the adrenergic endings and their relations with other processes and cells of the caudal mesenteric ganglion were studied in detail. The problem of the origin and physiological role of adrenergic nerve endings in this ganglion is discussed.Institute of Physiology, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 86–92, January–February, 1980.     

Role of different types of fibers of the infraorbital nerve in synaptic activation of masseter and digastric motoneurons

Postsynaptic potentials of motoneurons of the masseter and digastric muscles evoked by stimulation of the infraorbital nerve with a strength of between 1 and 10 thresholds were investigated in cats anesthetized with a mixture of chloralose and pentobarbital. Depending on their ability to be activated by low-threshold afferents of this nerve, motoneurons of the masseter were divided into two groups. Stimuli with a strength of 1.2–2.5 times above threshold for the most excitable fibers of the infraorbital nerve evoked short-latency EPSPs in the motoneurons of the first group; a further increase in stimulus strength (3–9 thresholds) led to the appearance of IPSPs with latent periods of 2.8–3.5 msec. Motoneurons of the second group responded to stimulation of the infraorbital nerve with a strength of 3–9 thresholds by IPSPs whose latent periods varied from 6 to 8 msec. Stimuli below 3 thresholds in strength evoked no responses in these motoneurons. Stimulation of the infraorbital nerve with pulses of between 1 and 2 thresholds in strength evoked EPSPs in digastric motoneurons, but an increase in the strength of stimulation led to action potential generation. The presence of many excitatory and inhibitory inputs formed by afferent fibers of different types evidently provides a basis for functional diversity of jaw-opening and jaw-closing reflexes.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 6, pp. 596–603, November–December, 1980.     

The effect of decentralisation or chronic hypogastric nerve stimulation in vivo on the innervation and responses of the guinea-pig vas deferens

Summary The physiological, pharmacological and morphological characteristics of guinea-pig vas deferens supplied by hypogastric nerves rendered inactive by decentralisation were compared with those of vas deferens in which the nerve supply had been chronically stimulated for 3–9 days using implanted electrodes. No change was seen in decentralised preparations prior to 7 days, but from 8–15 days, increased sensitivity to application of noradrenaline in vitro was observed, which was shown to be related to reduced transmitter uptake by nerve terminals as well as to an increase in postjunctional sensitivity; there was also increased fatigability 7–14 days following decentralisation. Continuous stimulation of hypogastric nerves at 2 Hz for 4–8 h daily for 4–8 days resulted in enhanced transmitter uptake and reduced responses to noradrenaline; this was associated with a slight increase in noradrenaline content and a faster adrenergic neuromuscular response with a shorter latency. No appreciable changes in nerve or muscle structure studied by electron microscopy were observed following decentralisation, but there was an increase of between 12.5 and 29.6% in the number of close (< 100 nm) neuromuscular junctions following chronic stimulation for 8 days.     

Effect of electromagnetic radiation of millimeter range on restoration of motor activity after impairment of the sciatic nerve in the rat

The effect of low-intensity (10–12 mW/cm²) amplitude-modulated electromagnetic radiation (EMR) with a wavelength of 8.1 mm on restoration of motor activity of hindlimb after the sciatic nerve had been crushed was studied in rats (only the injured area was radiated). The recovery was found to be significantly accelerated by EMR: after a seven-week-long treatment by EMR, the mean amplitude of the extensor force developed by the hindlimb of the EMR-treated animals reached 62.3% of its initial value (recorded before the nerve had been crushed), while in the control group of animals it was equal to near 40%.Neirofiziologiya/Neurophysiology, Vol. 28, No. 1, pp. 3–6, January–February, 1996.     

Effect of nociceptive stimulation of signal transmission from low-threshold cutaneous afferents in the somatosensory system

In cats anesthetized with chloralose nociceptive heating of the skin of the foot to 44–60°C led to a two- to fourfold increase in amplitude of primary cortical responses to direct stimulation of neurons of the spinocervical tract receiving information from the heated area of skin, but did not affect primary responses evoked by stimulation of axons of these neurons in the dorsolateral funiculus, and actually inhibited the response to stimulation of the nerve innervating the heated area of skin. Inhibition was accompanied by depolarization of central terminal of low-threshold fibers of this nerve: During heating the amplitude of the antidromic discharges evoked in the nerve by stimulation of its presynaptic endings in the spinal cord was increased two- to threefold. After abolition of presynaptic depolarization with picrotoxin (0.2–0.7 mg/kg, intravenously) or as a result of asphyxia, nociceptive heating acquired the ability to facilitate primary responses arising as a result of stimulation of the nerve also. The amplitude of the responses was increased under these circumstances by 3–20 times. It is concluded that acute nociceptive stimulation causes such powerful presynaptic inhibition of impulse transmission from low-threshold fibers of the cutaneous nerve that it virtually abolishes the facilitating effect of nociceptive impulses on sensory neurons of the spinal cord. It is suggested that it is this inhibitory mechanism which prevents the development of hyperalgesia during acute nociceptive stimulation.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 621–627, November–December, 1981.     

Some morphological and functional properties of the lateral line system of the dwarf catfish

The peripheral and central portions of the lateral line system of the dwarf catfish were studied by morphological and electrophysiological methods. The posterior lateral line nerve, innervating the electro- and mechanoreceptors of the trunk, was shown to consist of poorly myelinated fibers 2–9 µ in diameter. The conduction velocity in this nerve varied from 10 to 15 m/sec. The lateral line nerves end in the medial nucleus of the acoustico-lateral region, which consists of dorsal and medial parts. The former is composed of circular and triangular cells measuring 6–14 µ, the second part by circular cells measuring 4–6 µ. These parts of the medial nucleus are most sharply differentiated in the region of entry of the auditory nerve. Responses to stimulation of the lateral line electro- and mechanoreceptors were recorded over the whole of the acousticolateral region in the caudal-rostral direction. The neurons studied were located at depths of 400–800 µ in the region of the medial nucleus.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad, Translated from Neirofiziologiya, Vol. 7, No. 2, pp. 203–207, March–April, 1975.     

Chronic experimental study of natural activity of the dog splanchnic nerve by the pulsed coherent component separation method

Natural electrical activity in the left greater splanchnic nerve during feeding was studied in chronic experiments on dogs. The method of separation of coherent components in pulsed form was used to analyze the discharges: Recording from the nerve was carried out at two points; activity was delayed by the time for its conduction along the nerve between the channels, in the channel which received it first, and it was then led from both channels to the coincidence unit. Spontaneous afferent impulsation was shown to spread among a group of nerve fibers with conduction velocities of between 3.7 and 20 m/sec, and with a mean velocity for the maximum of activity of 9.2±1.0 m/sec. Efferent spontaneous activity was not detected. During feeding with meat, besides spontaneous activity, activity of a group of afferent fibers with conduction velocities within the range 3.7–9.2 m/sec also was found (the mean velocity for the maximum of activity was 5.8±0.7 m/sec), and also activity of a group of efferent fibers with conduction velocities within the range 2.5–9.8 m/sec (mean value for maximum 3.5±0.5 m/sec).A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 636–642, November–December, 1981.     

Diameters and conduction velocities of fibers in the cat auditory pathways

The diameters of nerve fibers in the brachium colliculi inferioris and geniculo-cortical tract were measured. The thickness of these fibers ranges from 0.5 to 6.0 µ, and in 82–88% of them it is 1.0–3.0 µ. About 100,000 nerve fibers were found in cross-sections through the brachium colliculi inferioris. The velocity of conduction along centripetal fibers of the geniculo-cortical tract was determined. It varied from 11 to 28.6 m/sec in different fibers, and in 71% of them it was between 15 and 22 m/sec. The composition of the fibers of the geniculo-cortical tract was compared relative to their thickness and conduction velocity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 6, pp. 608–611, November–December, 1972.     

Spike train structure following application of nociceptive potassium chloride solutions to the cat saphenous nerve

The structure of the spike train coding the nociceptive signal was investigated by a cross-correlation method. The action of nociceptive solutions of potassium chloride (125–1000 mM) on the saphenous nerve caused excitation of both myelinated and nonmyelinated fibers. The density of the spike train increased during the action of the stimulus up to a threshold sufficient for the appearance of nociceptive reflexes. The maximum of these reflexes coincided with the appearance of synchronous pulsations of discharges in the group of unmyelinated fibers. The nociceptive signal evoked by direct action of highly concentrated potassium chloride solutions on the nerve is thus coded by a high density of the spike train generated by the nerve fibers. Synchronous pulsations may be present in the spike train under these circumstances.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevski Gor'kii State University. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 598–605, November–December, 1977.     

Localization of neurons innervating the columellar muscles of the snail

The topographic arrangement of large and small neurons participating in the mechanism of the defensive reflex was studied in the circumesophageal nerve ring ofHelix pomatia by a modified retrograde cobalt ion transport method. Comparison of the results with those of previous electrophysiological investigations of the mechanism of the defensive relfex leads to the conclusion that this reflex is effected by a system of neurons consisting of nine large and 60–80 small nerve cells.Research Institute of Neurocybernetics, State University, Rostov-on-Don. Translated from Neirofiziologiya, Vol. 12, No. 6, pp. 637–641, November–December, 1980.     

Influence of L-serine-O-phosphate on synaptic transmission in afferent synapses of the ampullae of Lorenzini of skates

The method of superfusion of the basal membranes of the ampullae of Lorenzini of skates was used to investigate the influence of L-serine-O-phosphate (SOP) on the background and evoked activity of afferent nerve fibers, as well as on the effects of application of agonists: exciting amino acids — L-glutamate (L-GLU), kainate (KA), quisqualte (Q), and N-methyl-D-aspartate (NMDA). It was found that SOP (threshold concentration 10^–7 M) had an inhibiting effect on the background and evoked activity of the nerve fibers; depending on the concentration it decreased the stimulatory effects of L-GLU and NMDA and did not change the responses due to application of KA and Q. The data obtained suggest that the effects of SOP observed in the ampullae of Lorenzini are associated with its interaction with NMDA-type amino acid receptors.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 23, No. 4, pp. 387–391, July–August, 1991.     

Effect of preliminary mechanical and antidromic influences on orthodromic activity in C fibers from mechanoreceptors of the cat skin

Analysis of afferent activity in unmyelinated fibers of a cutaneous nerve was carried out by the colliding impulses method in cats. The effect of antidromic excitation of the nerve and mechanical stimulation of the receptors on subsequent orthodromic activity during stretching of the skin was investigated. Both these factors were shown to reduce subsequent orthodromic activity evoked by testing stimulation. The reduction in activity was greatest 10–15 sec after stimulation. The duration of the inhibitory effect was greater after mechanical than after antidromic stimulation. Combined mechanical stimulation and antidromic excitation resulted in a greater decrease of afferent activity and an increase in the time of its recovery. An increase in the frequency of antidromic excitation potentiated the inhibitory effect of preliminary stimulation on orthodromic activity in C fibers.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii Gor'kii State University. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 307–312, May–June, 1977.