Direct evidence for spinal cord microglia in the development of a neuropathic pain-like state in mice

The present study was undertaken to further investigate the role of glial cells in the development of the neuropathic pain-like state induced by sciatic nerve ligation in mice. At 7 days after sciatic nerve ligation, the immunoreactivities (IRs) of the specific astrocyte marker glial fibrillary acidic protein (GFAP) and the specific microglial marker OX-42, but not the specific oligodendrocyte marker O4, were increased on the ipsilateral side of the spinal cord dorsal horn in nerve-ligated mice compared with that on the contralateral side. Furthermore, a single intrathecal injection of activated spinal cord microglia, but not astrocytes, caused thermal hyperalgesia in naive mice. Furthermore, 5-bromo-2'-deoxyuridine (BrdU)-positive cells on the ipsilateral dorsal horn of the spinal cord were significantly increased at 7 days after nerve ligation and were highly co-localized with another microglia marker, ionized calcium-binding adaptor molecule 1 (Iba1), but neither with GFAP nor a specific neural nuclei marker, NeuN, in the spinal dorsal horn of nerve-ligated mice. The present data strongly support the idea that spinal cord astrocytes and microglia are activated under the neuropathic pain-like state, and that the proliferated and activated microglia directly contribute to the development of a neuropathic pain-like state in mice.     

Extrapyramidal descending influences on neurons of the spinal cord in a superreflexia state

The spinal superreflexia state was modeled in experiments on rats using preliminary transection of the spinal cord and injection (in the course of the acute experiment) of 4-aminopyridine. An extremely high (reaching 15–20 mV) amplitude of monosynaptic reflex discharges (MRs) evoked by stimulation of the dorsal root and recorded from the ventral root (VR) L ₄ and the presence of an additional component in the above discharges were phenomena indicative of the development of the above state. Under such conditions, the amplitudes of the discharges evoked in the VR by electrical stimulation of the round window of the labyrinth (vestibular stimulation) and of the discharges elicited by stimulation of the motor cortex under conditions of bilateral transection of the pyramids increased several times. Thresholds of the VR responses to vestibular and cortical stimulations demonstrated an about threefold drop; latencies of the mass responses and responses of single spinal moto-and interneurons decreased about twofold, on average. The pattern of vestibular conditioning effects on the VR MRs changed: in intact animals vestibular stimulation induced inhibition of the VR MRs, while in animals with superreflexia such stimulation led to facilitation of the MRs. Cortical stimulation under conditions of pyramidotomy in both intact animals and animals with superreflexia resulted in facilitation of the VR MRs of a nearly the same intensity. The levels of convergence of the segmental and supraspinal effects on interneurons and motoneurons of the rat spinal cord dramatically increased under superreflexia conditions. The possible mechanisms of augmentation of the descending influences on spinal neuronal systems under the above conditions are discussed. Neirofiziologiya/Neurophysiology, Vol. 38, No. 2, pp. 140–149, March–April, 2006.     

Post-translational modifications in the rat lumbar spinal cord in experimental autoimmune encephalomyelitis

Changes in protein methylation, citrullination, and phosphorylation during experimental autoimmune encephalomyelitis, a rodent model of multiple sclerosis, were evaluated using isobaric tags for relative and absolute quantification analysis of peptides produced from normal and diseased rat lumbar spinal cords. We observed alterations in the post-translational modification of key proteins regulating signal transduction and axonal integrity. Dephosphorylation of discrete serine residues within the neurofilament heavy subunit C-terminus was observed. We report for the first time elevated citrullination of Arg27 in glial fibrillary acidic protein, which may contribute to the pathophysiology of astrocytes.     

Peptidergic neuromodulation of the lumbar locomotor network in the neonatal rat spinal cord

It is now well established that a dynamic balance of neurotransmitters and neuromodulators finely influence the output of neuronal networks and subsequent behaviors. In the present study, to further understand the modulatory processes that control locomotor behavior, we investigated the action of 11 neuropeptides, chosen among the various peptide subfamilies, on the lumbar neuronal network in the in vitro neonatal rat spinal cord preparation. Peptides were bath-applied alone, in combination with N-methyl-D,L-aspartate (NMA) or with the classical 'locomotor cocktail' of NMA and serotonin. Using these different experimental paradigms, we show that each peptide can neuromodulate the lumbar locomotor network and that peptides exhibit different neuromodulatory profiles and potencies even within the same family. Only vasopressin, oxytocin, bombesin and thyrotropin releasing hormone triggered tonic or non-organized rhythmic activities when bath-applied alone. All the neuropeptides modulated NMA induced activity and/ or ongoing sequences of fictive locomotion to varying degrees. These results suggest that neuropeptides play an important role in the control of the neural network for locomotion in the neonatal rat. Their various profiles of action may account in part for the great flexibility of motor behaviors.     

Transmission in the sensorimotor synapses of the lumbar spinal cord in Rana ridibunda tadpoles

In experiments on preparations of isolated spinal cord of the tadpoles, intracellular studies have been made on the synaptic potentials evoked in the lumbar motoneurones during total activation of the fibers within the 9th dorsal root. It was shown that primary afferents form monosynaptic contacts with motoneurones at stages XIV-XXV. During larval development, the number of motor cells in which monosynaptic EPSPs are recorded increases, whereas the number of motoneurones with only polysynaptic reactions decreases. From the moment of formation of monosynaptic contacts, transmission in direct sensory-motor synapses is realised by a dual (electrical-chemical) mode. The data obtained are discussed in relation to the problem of evolution of synaptic transmission between heterotypic neurones in vertebrates.     

Properties of axons of sympathetic preganglionic neurons in the cat lumbar spinal cord

Responses arising in ventral root filaments and antidromic discharges of single sympathetic preganglionic neurons in the lateral horn of gray matter in segment L₂ of the cat spinal cord were recorded during stimulation of the white rami communicantes in the same segment. Conduction velocities, thresholds, and refractory periods were determined for individual groups of sympathetic preganglionic fibers. Excitation was conducted more slowly along the intramedullary part of the axons of some sympathetic neurons than along the extramedullary part. In a third group of neurons studied the second antidromic discharge appeared in response to paired stimulation if the interstimulus interval was appreciably longer than their refractory period. It is postulated that axons of sympathetic preganglionic neurons in the lumber spinal cord have a thin intramedullary part and are supplied with recurrent collaterals.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 6, No. 2, pp. 143–151, March–April, 1974.     

Protective effect of pioglitazone on morphine-induced neuroinflammation in the rat lumbar spinal cord

Background

Morphine-induced tolerance is associated with the spinal neuroinflammation. The aim of this study was to explore the effects of oral administration of the pioglitazone, the peroxisome proliferator activated receptor gamma (PPAR-γ) agonist, on the morphine-induced neuroinflammation in the lumbar region of the male Wistar rat spinal cord.

Results

Co-administration of the pioglitazone with morphine not only attenuated morphine-induced tolerance, but also prevented the up-regulation of pro-inflammatory cytokines (tumor necrosis factor alpha, interleukin-1beta, and interleukin 6) and nuclear factor-kappa B activity. Administration of the GW-9662 antagonized the above mentioned effects of the pioglitazone.

Conclusions

It is concluded that oral administration of the pioglitazone attenuates morphine-induced tolerance and the neuroinflammation in the lumbar region of the rat spinal cord. This action of the pioglitazone may be, at least in part, due to an interaction with the spinal pro-inflammatory cytokine expression and the nuclear factor-kappa B activity.     

Increased number of neurons in the cervical spinal cord of aged female rats

In the brain, specific signaling pathways localized in highly organized regions called niches allow the persistence of a pool of stem and progenitor cells that generate new neurons in adulthood. Much less is known about the spinal cord where a sustained adult neurogenesis is not observed. Moreover, there is scarce information concerning cell proliferation in the adult mammalian spinal cord and virtually none in aging animals or humans. We performed a comparative morphometric and immunofluorescence study of the entire cervical region (C1-C8) in young (5 mo.) and aged (30 mo.) female rats. Serum prolactin (PRL), a neurogenic hormone, was also measured. Gross anatomy showed a significant age-related increase in size of all of the cervical segments. Morphometric analysis of cresyl violet stained segments also showed a significant increase in the area occupied by the gray matter of some cervical segments of aged rats. The most interesting finding was that both the total area occupied by neurons and the number of neurons increased significantly with age, the latter increase ranging from 16% (C6) to 34% (C2). Taking the total number of cervical neurons the age-related increase ranged from 19% (C6) to 51% (C3), C3 being the segment that grew most in length in the aged animals. Some bromodeoxyuridine positive-neuron specific enolase negative (BrdU(+)-NSE(-)) cells were observed and, occasionally, double positive (BrdU(+)-NSE(+)) cells were detected in some cervical segments of both young and aged rats groups. As expected, serum PRL increased markedly with age. We propose that in the cervical spinal cord of female rats, both maturation of pre-existing neuroblasts and/or possible neurogenesis occur during the entire life span, in a process in which PRL may play a role.     

Polarization of primary afferent terminals in the lumbar spinal cord during fictitious locomotion

Changes in electrical polarization of primary afferent terminals in the lumbosacral portion of the spinal cord were investigated during fictitious locomotion in immobilized decorticated and spinal cats. Fictitious locomotion was accompanied by stable hyperpolarization of the afferent terminals, against the background of which they were periodically depolarized in rhythm with efferent activity. These tonic and phasic changes were observed in terminals of all groups of afferent fibers tested: cutaneous and muscular (Ia and Ib). Periodic in-phase depolarization was carried out in different ipsilateral segments of the lumbosacral enlargement. During ficitious galloping changes in depolarization of the primary efferents were in phase on different sides; during fictitious walking, these periodic changes were out of phase. On the basis of these results the physiological importance of changes in electrical polarization of primary afferent terminals of the spinal locomotor generator is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 481–489, September–October, 1980.     

Canine spinal cord energy state after in situ freezing

[Methyl-³H]choline has been injected intraventricularly into adult rabbits, and the rate of synthesis of phosphatidylcholine, choline plasmalogen and sphingomyelin (and their hydrosoluble precursors) in isolated neuronal and glial cells has been investigated. At all time intervals examined, the injected radioactivity was incorporated only into the base moiety of the choline lipids in both cell types. Maximum labelling of the two choline phosphoglycerides occurred in neurons 150 min after administration, whereas the highest specific radioactivity for glial phosphatidylcholine and choline plasmalogen was reached at 6 and 10 h, respectively. At any time interval examined, the neuronal and glial choline plasmalogen displayed a higher specific radioactivity than the corresponding diacyl-derivative. The two phosphoglycerides incorporated the base in both cell populations at a faster rate than did whole brain tissue. Sphingomyelin was labelled in both cells at a low rate and acquired measurable radioactivity levels only after 2 h from isotope administration. Highest levels of radioactivity for phosphorylcholine and cytidine-5′-diphosphocholine were reached in both neurons and glia 1-2 h after administration, but these levels per unit protein were higher in glial than in neuronal cells.     

Physiologic evidence for descending tryptaminergic pathways in the spinal cord.

LSD was more effective in facilitating the flexor reflex in the chronic than in the acute spinal dog. On the other hand, $\text{1}$-tryptophan produced a significant facilitation of the flexor reflex in the acute spinal dog but not in the chronic spinal dog. These data are consistent with the hypothesis that there are long descending tryptaminergic axons which have the capacity of converting tryptophan to tryptamine and releasing it in the vicinity of post-synaptic facilitatory receptors which degenerate in the chronic spinal dog.     

Descending neuronal projections to the lumbar segment of the spinal cord of cats

In the experiments, performed on cats by means of retrograde axonal horseradish peroxidase transport, localization of the sources of descending supra- and propriospinal projections to the area of the lumbar parts of the spinal cord, where the generator of locomotor movements is located. After local administration of horseradish peroxidase into the spinal cord, the greatest amount of the labelled neurons is observed in the ipsilateral reticular formation and in the Koelliker-Fuse nucleus. Comparison of the number of neurons, forming the descending projections from the I cervical up to the IV lumbar segments demonstrates an essential predominance of short propriospinal connections over the long, as well as over the supraspinal ones.     

ABRA在不同年龄大鼠腰段脊髓中的表达变化

目的检测Actin binding Rho activator（ABRA）在不同年龄大鼠腰段脊髓中的表达变化。方法采用Western blot定量检测不同年龄大鼠腰段脊髓中ABRA蛋白水平表达变化,采用免疫荧光染色显示不同年龄大鼠腰髓中ABRA细胞定位。结果Western blot显示ABRA在新生鼠腰段脊髓中表达显著高于成年鼠及老年鼠。免疫荧光染色显示ABRA广泛表达于神经元的胞核、胞浆和突起,在腰髓前角,与前角运动神经元存在共定位,在腰髓后角,与小的NeuN阳性感觉神经元存在共定位。腰髓前角、后角的阳性细胞计数均显示新生鼠ABRA＋NeuN双阳性细胞占总ABRA阳性细胞百分比显著低于成年鼠及老年鼠。结论ABRA广泛表达于腰髓中的神经元,ABRA在新生鼠腰髓中表达最强,随年龄的增长呈现明显的时相变化,提示ABRA可能参与了腰髓中神经元的发育和成熟。     

Effects of ischemia on opioid receptors in newborn pig lumbar spinal cord

The characteristics of opioid receptors were studied by the binding of (3H)naloxone in ischemic lumbar spinal cord segments of newborn pigs. Ischemia was elicited by ligating the aorta for 30 min. The number of millimicron opioid receptors decreased, from 117 +/- 18 to 89 +/- 11 fmol/mg protein, while the Kd value was not significantly altered. It is concluded that even a relatively brief interruption of the oxygen supply may cause severe damage in the lumbar spinal cord of the newborn pig, affecting the opioid neurotransmission. The animal model employed here might be suitable for studying the effects of hypoxia in newborns and children during chest operations involving the descending aorta.