Decreased Uptake and Release of D-Aspartate in the Guinea Pig Spinal Cord After Partial Cordotomy

This study attempts to determine if L-glutamate and/or L-aspartate may be transmitters of neural tracts descending from the brain to the spinal cord. The uptake and electrically evoked release of D-[3H]aspartate, a putative marker for L-glutamate and L-aspartate, were measured in the cervical enlargement of the guinea pig spinal cord. These activities were compared using unlesioned animals and others with a lesion on the right side of the spinal cord. Partial cordotomy (segment C5) produced a heavy loss of descending fibers, a small loss of primary sensory fibers, and a depression of the uptake and the Ca2+ -dependent, electrically evoked release of D-aspartate ipsilateral and caudal to the lesion. Contralaterally, there was a moderate loss of corticospinal fibers, some loss of other descending axons, and a depression of D-aspartate release. Dorsal rhizotomy (segments C4-T1) produced a heavy loss of primary sensory fibers ipsilateral to the lesion. Ipsilaterally, but not contralaterally, the uptake and release of D-aspartate were depressed. Degeneration after partial cordotomy in combination with dorsal rhizotomy was assumed to be the sum of that produced by each lesion separately. This combined lesion depressed D-aspartate uptake ipsilaterally and depressed D-aspartate release on both sides of the cervical enlargement. None of the lesions altered the uptake and the evoked release of [3H]GABA. These findings support the hypothesis that the synaptic endings of one or more neural tracts descending from the brain to the spinal cord mediate the uptake and release of D-aspartate and, therefore, may use L-glutamate or L-aspartate as a transmitter.     

Extracellular Amino Acid Concentrations in the Dorsal Spinal Cord of Freely Moving Rats Following Veratridine and Nociceptive Stimulation

In vivo microdialysis was used to sample extracellular concentrations of amino acids in the dorsal lumbar spinal cord of freely moving rats. Changes in the extracellular concentrations of amino acids were measured in response to infusion of veratridine (180 microM), a sodium channel activator, as well as during acute noxious stimulation by an injection of 5% formalin into the metatarsal region of the hindleg. Veratridine produced a tetrodotoxin (TTX)-sensitive increase in the extracellular concentration of Glu. Concentrations of Asp, taurine, Ala, Asn, and Gly were not significantly elevated following veratridine stimulation. Intradermal injection of formalin produced a TTX-sensitive increase in Asp concentration and a non-TTX-sensitive increase in Glu concentration. These data support the hypothesis that Glu and Asp are dorsal horn neurotransmitters involved in nociception.     

Decreased Release of D-Aspartate in the Guinea Pig Spinal Cord After Lesions of the Red Nucleus

This study attempts to determine if fibers that project from the guinea pig red nucleus to the spinal cord use L-glutamate and/or L-aspartate as transmitters. Unilateral injections of kainic acid were placed stereotaxically in the red nucleus to destroy the cells of origin of the rubrospinal tract. Six days after the injection, Nissl-stained sections through the lesion site showed that the majority of neurons in the red nucleus ipsilateral to the kainic acid injection were destroyed. In addition, the lesioned area included parts of the surrounding midbrain reticular formation. Silver-impregnated, transverse sections of the cervical spinal cord revealed the presence of degenerating fibers contralaterally in laminae IV-VII of the gray matter. Ipsilaterally, very sparse degeneration was evident in laminae VII and VIII of the gray matter. Two to six days after surgery, the electrically evoked, Ca2(+)-dependent release of both D-[3H]aspartate, a marker for glutamatergic/aspartatergic neurons, and gamma-amino[14C]-butyric acid ([14C]GABA) was measured in dissected quadrants of the spinal cervical enlargement. Lesions centered on the red nucleus depressed the release of D-[3H]aspartate by 25-45% in dorsal and ventral quadrants of the cervical enlargement contralaterally. The release of [14C]GABA was depressed by 27% in contralateral ventral quadrants. To assess the contribution of rubro- versus reticulospinal fibers to the deficits in amino acid release, unilateral injections of kainic acid were placed stereotaxically in the midbrain reticular formation lateral to the red nucleus. Nissl-stained sections through the midbrain revealed the presence of extensive neuronal loss in the midbrain and rostral pontine reticular formation, whereas neurons in the red nucleus remained undamaged. In the spinal cord, degenerating axons were present ipsilaterally in laminae VII and VIII of the gray matter. Some fiber degeneration was also evident contralaterally in laminae V and VI of the gray matter. This lesion did not affect the release of either D-[3H]aspartate or [14C]GABA in the spinal cord. The substantial decrements in D-[3H]aspartate release following red nucleus lesions suggests that the synaptic endings of rubrospinal fibers mediate the release of D-[3H]aspartate in the spinal cord. Therefore, these fibers may be glutamatergic and/or aspartatergic. Because other evidence suggests that rubrospinal neurons are probably not GABAergic, the depression of [14C]GABA release probably reflects changes in the activity of spinal interneurons following the loss of rubrospinal input.     

Evidence for Ascending and Descending Intraspinal as Well as Primary Sensory Somatostatin Projections in the Rat Spinal Cord

Somatostatin distribution was measured quantitatively in the rat spinal cord by radioimmunoassay. Rostro-caudally, somatostatin content was about 50% higher in lumbar-sacral cord than in cervical or thoracic levels. The dorso-ventral distribution is more uneven: somatostatin is highest in the dorsal horn, where the peptide is 15 times as concentrated as it is in the ventral white matter, the region of lowest concentration. However, measurable amounts of the peptide were found in all regions studied. Dorsal root ganglionectomy decreased somatostatin levels in the dorsal cord, supporting the previously proposed role for this peptide as a primary sensory neurotransmitter or modulator; but somatostatin content also was decreased both rostral and caudal to spinal transection, indicating the presence of ascending and descending somatostatin pathways within the spinal cord. Brain levels did not change. Met-enkephalin and substance P were also measured after the above surgical manipulations. Met-enkephalin content was not altered and substance P content was lowered significantly only after ganglionectomy. Although this study confirms the primary sensory neuron as the origin of a part of spinal cord somatostatin, it further indicates the presence of ascending and descending somatostatin pathways within the rat spinal cord.     

Changes in Amino Acid Contents in the Spinal Cord and Brainstem of Rats with Experimental Autoimmune Encephalomyelitis

The effects of experimental autoimmune encephalomyelitis (attack and recovery) on levels of six amino acids have been investigated in nine regions of the Lewis rat spinal cord between segments C3 and Co1 and in the brainstem. Amino acids were analyzed by separation of their 4'-dimethylaminoazobenzene-4-sulfonyl chloride derivatives on a reversed-phase column using a ternary gradient. Glutamate and gamma-aminobutyric acid were reduced by 10-30% in all segments during the attack, whereas taurine, lysine, glutamine, and glycine were all greatly increased (up to 300%). Most values except those of taurine, as well as glutamate in certain segments, returned to normal on recovery. Because some of these compounds have neurotransmitter function, these changes may contribute to the neurological symptoms of experimental autoimmune encephalomyelitis.     

D-Aspartate Uptake and Release in the Guinea Pig Spinal Cord After Partial Ablation of the Cerebral Cortex

This study attempts to determine if L-glutamate and L-aspartate may be transmitters of the guinea pig corticospinal tract. Unilateral ablations were made of the frontal and parietal neocortex which destroyed most of the motor and somatosensory areas in the right cerebral hemisphere. In lesioned animals, transverse sections of the cervical enlargement of the spinal cord (segments C6--T1) were stained to reveal degenerating fibers. Degeneration of axons first appeared 4 days after surgery, reached a maximum on the seventh day, and began to wane by the ninth day. The most prominent loss of axons appeared deep in the dorsal funiculus and in laminae IV-IX of the gray matter contralateral to the cortical lesion. Ipsilaterally, there was very sparse degeneration of fibers in the dorsal and ventral funiculi and in the spinal gray matter. The uptake and release of D-[3H]aspartate, a putative nonmetabolizable marker for L-glutamate and L-aspartate, were measured in dissected quadrants of the cervical enlargement taken from intact and lesioned animals. The uptake and the electrically evoked, Ca2+-dependent release of D-[3H]aspartate were depressed by 29-35% at 4 and 7 days after surgery, but only in tissue that was contralateral to the cortical ablation. The lesion had no effect on the uptake and release of exogenous gamma-[14C]aminobutyric acid, which were measured as indices of the postlesion integrity of neurons in the spinal gray matter. These findings suggest that the synaptic endings of corticospinal fibers probably mediate the uptake and release of D-[3H]aspartate and, therefore, may use L-glutamate and/or L-aspartate as a transmitter.     

Effects of Methylprednisolone on Extracellular Lactic Acidosis and Amino Acids After Severe Compression Injury of Rat Spinal Cord

Abstract: We evaluated in rats with severe spinal cord compression at T8–9 the influence of methylprednisolone (MP) on lactic acidosis and extracellular amino acids, which may cause secondary, perifocal injuries of the cord. MP (30 mg/kg) was given intravenously 30 min before compression and hourly thereafter (15 mg/kg). Other rats with compression, given saline, served as controls. Samples from the extracellular fluid of one dorsal horn were collected by microdialysis and analyzed by HPLC. Microdialysis was performed for 1.5 h to establish basal levels. Samples were collected for 3 h after compression. MP-treated rats showed a reduction of dialysate lactic acid and arginine levels during the first 1–2 h after trauma. The mean dialysate levels of glutamate in MP-treated rats were lower than those of the controls, but the difference was not statistically significant. MP treatment did not influence dialysate levels of aspartate, glutamine, histidine, glycine, threonine, taurine, alanine, GABA, and tyrosine. Our study shows that MP has several effects, including reduced lactic acid formation, reduced levels of arginine (the substrate for nitric oxide production), and a trend toward decreased extracellular accumulation of the excitotoxic amino acid glutamate. We conclude that MP has the capacity to change the composition of the extracellular edema fluid after trauma to the spinal cord. These changes may counteract free radical formation and may be important mechanisms by which MP exerts its beneficial actions.     

Enzyme Immunoassay for Tachykinin-Like Immunoreactivity in the Guinea Pig Spinal Cord

A solid-phase enzyme immunoassay for quantitation of tachykinin-like immunoreactivity (TK-LI) is presented. Because the antiserum K-12 recognizes various tachykinins, such as neurokinin A (100%), kassinin (103%), eledoisin (51%), neurokinin B (18%), physalaemin (0.7%), and substance P (0.7%), the immunoreactivity detected in this enzyme immunoassay has been termed TK-LI. The assay was performed on 96-well microtiter plates coated with a mouse monoclonal second antibody. After preincubation of soluble neurokinin A or samples and K-12 antiserum for 3 h at room temperature, acetylcholinesterase-labelled neurokinin A was allowed to react overnight at 4 degrees C. Samples were finally incubated with Ellman's reagent for 2 h and the absorbance was measured at 414 nm. The threshold for detection of TK-LI was 2 fmol/well. TK-LI release from guinea pig dorsal spinal cord slices was evoked by capsaicin or high K+ medium. The capsaicin-evoked TK-LI release was increased in the presence of thiorphan, but not in that of captopril.     

Effects of Peripheral Axotomy on Cholecystokinin Neurotransmission in the Rat Spinal Cord

Abstract : Because cholecystokinin (CCK) acts as a "functional" endogenous opioid antagonist, it has been proposed that changes in central CCKergic neurotransmission might account for the relative resistance of neuropathic pain to the analgesic action of morphine. This hypothesis was addressed by measuring CCK-related parameters 2 weeks after unilateral sciatic nerve section in rats. As expected, significant decreases (-25-38%) in the tissue concentrations and in vitro release of both substance P and calcitonin gene-related peptide were noted in the dorsal quadrant of the lumbar spinal cord on the lesioned side. In contrast, the tissue levels and in vitro release of CCK were unchanged in the same area in lesioned rats. Measurements in dorsal root ganglia at L4-L6 levels revealed no significant changes in proCCK mRNA after the lesion. However, sciatic nerve section was associated with a marked ipsilateral increase in both CCK-B receptor mRNA levels in these ganglia (+70%) and the autoradiographic labeling of CCK-B receptors by [³H]pBC 264 (+160%) in the superficial layers of the lumbar dorsal horn. Up-regulation of CCK-B receptors rather than CCK synthesis and release probably contributes to increased spinal CCKergic neurotransmission in neuropathic pain.     

Effect of Lesions of the Olfactory Bulb on the Levels of Amino Acids and Related Enzymes in the Olfactory Cortex of the Guinea Pig

Abstract: Olfactory bulb removal and consequential degeneration of the lateral olfactory tract led to a decreasein the levels of glutaminase and malate dehydrogenase inthe ipsilateral olfactory cortex. These changes in enzyme activity may account for the well established decrease inthe levels of aspartate and glutamate in the olfactory cortex following ipsilateral bulbectomy. The level of glutamine synthetase, a glial marker enzyme, was slightly-increased while the activities of glutamate decarboxylase, glutamate dehydrogenase, and glutamate oxaloacetic transaminase were unchanged.     

Effect of Impact Trauma on Neurotransmitter and Nonneurotransmitter Amino Acids in Rat Spinal Cord

N-Methyl-D-aspartate (NMDA) administration exacerbates neurological dysfunction after traumatic spinal cord injury in rats, whereas NMDA antagonists improve outcome in this model. These observations suggest that release of excitatory amino acids contributes to secondary tissue damage after traumatic spinal cord injury. To further examine this hypothesis, concentrations of free amino acids were measured in spinal cord samples from anesthetized rats subjected to various degrees of impact trauma to the T9 spinal segment. Levels of excitatory and inhibitory neurotransmitter amino acids [gamma-aminobutyric acid (GABA), glutamate, aspartate, glycine, taurine] and levels of nonneurotransmitter amino acids (asparagine, glutamine, alanine, threonine, serine) were determined at 5 min, 4 h, and 24 h posttrauma. Uninjured surgical (laminectomy) control animals showed modest but significant declines in aspartate and glutamate levels, but not in other amino acids, at all time points. In injured animals, the excitatory amino acids glutamate and aspartate were significantly decreased by 5 min posttrauma, and remained depressed at 4 h and 24 h as compared with corresponding laminectomy controls. In contrast, the inhibitory amino acids, glycine, GABA, and taurine, were decreased at 5 min postinjury, had partially recovered at 4 h, and were almost fully recovered at 24 h. The nonneurotransmitter amino acids were unchanged at 5 min posttrauma and significantly increased at 4 h, with partial recovery at 24 h. At 4 h postinjury, severe trauma caused significantly greater decreases in aspartate and glutamate than did either mild or moderate injury. These findings are consistent with the postulated role of excitatory amino acids in CNS trauma.     

Preparation of Neurofilament Protein from Guinea Pig Peripheral Nerve and Spinal Cord

Abstract: A simple and rapid method for preparation of enriched neurofilament protein from mammalian peripheral nerve or spinal cord is described. Tissue extracts from guinea pig nerve or spinal cord are fractionated by ammonium sulfate fractionation, chromatography on Sepharose 4B, and precipitation with ethanol. Molecular exclusion chromatography on Sepharose 4B, in which the neurofilament protein elutes quantitatively in the exclusion volume of the column, with little contamination by other proteins, is found to be a highly effective purification step. The protein is found to precipitate in ammonium sulfate fractions over a wide range of salt concentration, from 20 to 80% saturation. It is found to be quantitatively precipitated in 40% v/v ethanol-water. The preparative method described yields 0.25 mg of neurofilament protein per gram of nerve or spinal cord, with a purity of approximately 50%. The three principal neurofilament polypeptides, which have molecular weights by SDS-polyacrylamide gel electrophoresis of 200K, 145K, and 68K, are found to be present in the preparation in a molar ratio of 1:2:6. A variant form of neurofilament protein occurring in approximately 20% of Hartley strain guinea pigs is described, which has the polypeptide composition: 200K, 192K, 145K, 68K.     

Alterations of Amino Acid Transmitter Systems in Spinal Cords of Chronic Paraplegic Dogs

The high-affinity uptake of [3H]serotonin, [3H]glutamate, and [3H]gamma-aminobutyric acid [( 3H]GABA) and the Na+-independent binding of [3H]glutamate and [3H]GABA were studied using spinal cord preparations obtained from normal mongrel dogs and from dogs made paraplegic by midthoracic spinal cord crush. Lumbosacral regions of the spinal cord were removed either before (1 week) or after (3 to 8 weeks) onset of spasticity. A myelin-free synaptosomal fraction was obtained by centrifugation and used for studying high-affinity uptake and for preparing synaptic plasma membranes for Na+-independent binding experiments. For the paraplegic groups, the uptake of 30 nM [3H]serotonin was 66 and 18% of control values after 1 and 3 weeks, respectively. Eadie-Hofstee analysis of [3H]serotonin uptake showed a 90% reduction in Vmax for the paraplegic group relative to control values, thereby indicating the expected loss of descending serotonergic pathways. The high-affinity uptakes of 1 microM [3H]glutamate and [3H]GABA were the same in both the control and nonspastic paraplegic groups after 1 week. However, after 3 weeks, the uptakes of [3H]glutamate and [3H]GABA were 60-70% higher for the spastic group than for the control animals. For both amino acids, Eadie-Hofstee plots revealed no difference in Km and higher Vmax for the spastic group relative to control values. After 1 and 3 weeks, the Na+-independent binding of 5 nM [3H]glutamate was 40-85% higher and the binding of 10 nM [3H]GABA was 40-60% lower for the paraplegic groups relative to the values for the control animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Spinal Morphine Administration Reduces the Fatty Acid Contents in Spinal Cord and Brain by Increasing Oxidative Stress

It is well known that oxidative stress damages bimolecules such as DNA and lipids. No study is available on the morphine-induced oxidative damage and fatty acids changes in brain and spinal tissues. The aim of this work was to determine the effects of morphine on the concentrations and compositions of fatty acid in spinal cord segments and brain tissues in rabbits as well as lipid peroxidation (LP) and glutathione (GSH) levels in cortex brain. Twelve New Zealand albino rabbits were used and they were randomly assigned to two groups of 6 rabbits each. First group used as control although morphine administrated to rats in second group. Cortex brain and (cervical, thoracic, lumbar) samples were taken. The fatty acids between n:18.0 and 21.0 were present in spinal cord sections and n:10 fatty acids in control animals were present in the brain tissues. Compared to n:20.0–24.0 fatty acids in spinal cord sections and 8.0 fatty acids in the brain tissues of drug administered animals. The concentration and composition of the fatty acid methyl esters in spinal cord and brain tissues was decreased by morphine treatments. LP levels in the cortex brain were increased although GSH levels were decreased by the morphine administration. In conclusion, unsaturated fatty acids contents in brain and spinal cord sections and GSH were reduced by administrating spinal morphine although oxidative stress as LP increased. The inhibition oxidative damage may be a useful strategy for the development of a new protection for morphine administration as well as opiate abuse.     

Stem Cells Downregulate the Elevated Levels of Tissue Plasminogen Activator in Rats After Spinal Cord Injury

We investigated the involvement of tPA after SCI in rats and effect of treatment with human umbilical cord blood derived stem cells. tPA expression and activity were determined in vivo after SCI in rats and in vitro in rat embryonic spinal neurons in response to injury with staurosporine, hydrogen peroxide and glutamate. The activity and/or expression of tPA increased after SCI and reached peak levels on day 21 post-SCI. Notably, the tPA mRNA activity was upregulated by 310-fold compared to controls on day 21 post-SCI. As expected, MBP expression is minimal at the time of peak tPA activity and vice versa. Implantation of hUCB after SCI resulted in the downregulation of elevated tPA activity/expression in vivo in rats as well as in vitro in spinal neurons. Our results demonstrated the involvement of tPA in the secondary pathogenesis after SCI as well as the therapeutic potential of hUCB.     

Uptake and Release of γ-Aminobutyric Acid in the Guinea Pig Cochlear Nucleus After Axotomy of Cochlear and Centrifugal Fibers

Abstract: This study attempts to determine if γ-aminobutyric acid (GABA) may be a transmitter of cochlear nerve fibers projecting from the cochlea to the cochlear nucleus, and of centrifugal fibers projecting to the cochlear nucleus via the trapezoid body and the acoustic striae of the medulla. The uptake and the electrically evoked release of exogenous [¹⁴C]GABA were measured, in vitro, in the three major subdivisions of the guinea pig cochlear nucleus: the anteroventral, posteroventral, and dorsal cochlear nuclei. These activities were compared using unlesioned animals, animals with bilateral cochlear ablations, and animals whose trapezoid body and acoustic striae were interrupted on the right side of the medulla. Subdivisions from unlesioned animals took up [¹⁴C]GABA, achieving concentrations in the tissues that were 11–19 times that in the medium. Electrical stimulation evoked a Ca²⁺-dependent release of [¹⁴C]GABA from each subdivision. Bilateral cochlear ablation, which presumably destroyed the cochlear nerve fibers, had no effect on [¹⁴C]GABA uptake and release. Section of the trapezoid body and the acoustic striae on the right side of the medulla typically severed all known connections of the right posteroventral and dorsal cochlear nuclei with the rest of the brain, but left intact many connections involved with the right anteroventral cochlear nucleus. This lesion partially depressed [¹⁴C]GABA uptake and release in the right posteroventral and dorsal cochlear nuclei, but not in the right anteroventral cochlear nucleus. These findings suggest that one or more of the centrifugal tracts projecting to the cochlear nucleus may be GABAergic, 88% or more of the cochlear nerve fibers probably are not GABAergic, and some neurons of the cochlear nucleus are probably GABAergic.     

Tryptophan Overload in the Pregnant Rat: Effect on Brain Amino Acid Levels and In Vitro Protein Synthesis

The concentration of most amino acids was higher in the brains of 19- and 21-day rat fetuses than in their respective mothers. After an intraperitoneal load of tryptophan to the mother, the intracerebral concentration of several amino acids (including leucine) decreased not only in the mothers, but also in their fetuses. The in vitro incorporation of pHJleucine into proteins in brain postmitochondrial supernatant fractions was enhanced in both the mothers and fetuses after tryptophan administration, but this effect disappeared when protein synthesis was calculated by using specific activities corrected for the amount of unlabeled leucine in the preparation. By this criterion, protein synthesis activity appeared similar in the brains of 19- and 21-day pregnant rats but was higher in their fetuses, especially in the 21-day subjects. Thus, protein synthesis in the brain was not altered by marked changes in the amino acid pool and more profound and prolonged metabolic disturbances must occur to cause permanent damage in the developing brain.     

Uptake and Release of Glycine in the Guinea Pig Cochlear Nucleus After Axotomy of Afferent or Centrifugal Fibers

Glycine may be an inhibitory transmitter in the mammalian cochlear nucleus (CN). This study attempts to determine if cochlear and/or centrifugal projections to the CN use glycine as a transmitter. The high-affinity uptake and electrically evoked release of exogenous [14C]glycine were measured in vitro in the three major subdivisions of the guinea pig CN: the anteroventral, posteroventral, and dorsal cochlear nuclei (AVCN, PVCN, and DCN, respectively). [14C]Glycine (3.4 microM) was taken up by each subdivision, reaching tissue concentrations six to seven times that in the medium. Subsequent electrical stimulation evoked a Ca2+-dependent release of [14C]glycine from each subdivision. These activities were compared in subdivisions fr0m unlesioned animals, and from animals with lesions of centrifugal or cochlear projections to the CN. Two knife-cut lesions were made to interrupt centrifugal projections to the CN lying in the right acoustic striae and trapezoid body. In one group of animals, centrifugal fibers projecting mainly to the right AVCN and PVCN were severed, which reduced [14C]glycine uptake and release by 44-53% in these subdivisions, but not in the right DCN. In another group of animals, fibers projecting mainly to the right PVCN and DCN were severed, which reduced [14C]glycine uptake and release by 33-47% in these subdivisions, but not in the right AVCN. In CN subdivisions contralateral to either lesion there was no significant change in [14C]glycine uptake or release. Neither of these lesions altered the uptake or release of D-[3H]aspartate in the right or the left CN. Ablation of the left cochlea, which presumably destroyed cochlear nerve fibers unilaterally, had no effect on [14C]glycine uptake and release. These observations suggest that centrifugal projections contribute a proportion of the glycinergic synaptic endings in the CN. In addition, some glycinergic endings probably arise from neurons intrinsic to the CN. The cochlear nerve contains very few, if any, glycinergic fibers.     

NT-3 Expression in Spared DRG and the Associated Spinal Laminae as well as Its Anterograde Transport in Sensory Neurons Following Removal of Adjacent DRG in Cats

Neurotrophin-3 plays an important role in survival and differentiation of sensory and sympathetic neurons, sprouting of neurites, synaptic reorganization, and axonal growth. The present study evaluated changes in expression of NT-3 in the spinal cord and L6 dorsal root ganglion (DRG), after ganglionectomy of adjacent dorsal roots in cats. NT-3 immunoreactivity increased at 3 days post-operation (dpo), but decreased at 10 dpo in spinal lamina II after ganglionectomy of L1–L5 and L7–S2 (leaving L6 DRG intact). Conversely, NT-3 immunoreactivity decreased on 3 dpo, but increased on 10 dpo in the nucleus dorsalis. Very little NT-3 mRNA signal was detected in the spinal cord, despite the changes in NT-3 expression. The above changes may be related to changes in NT-3 expression in the DRG. Ganglionectomy of L1–L5 and L7–S2 resulted in increase in NT-3 immunoreactivity and mRNA in small and medium-sized neurons, but decreased expression in large neurons of L6 DRG at 3 dpo. It is possible that increased NT-3 in spinal lamina II is derived from anterograde transport from small- and medium-sized neurons of L6 DRG, whereas decreased NT-3 immunoreactivity in the nucleus dorsalis is due to decreased transport of NT-3 from large neurons in the DRG at this time. This notion is supported by observations on NT-3 distribution in the dorsal root of L6 after ligation of the nerve root. The above results indicate that DRG may be a source of neurotrophic factors such as NT-3 to the spinal cord, and may contribute to plasticity in the spinal cord after injury.     

Amino Acid Levels in the Cerebrospinal Fluid of Newly Diagnosed Epileptic Patients: Effect of Vigabatrin and Carbamazepine Monotherapies

Abstract: We studied the CSF amino acid levels of 42 patients with newly diagnosed epilepsy before treatment with antiepileptic medication and during monotherapy with either vigabatrin or carabamzepine. The present study shows that patients with newly diagnosed epilepsy have elevated levels of the excitatory amino acid glutamate in CSF. Vigabatrin monotherapy effectively prevents the appearance of seizures in patients with high baseline CSF glutamate levels. In these patients, vigabatrin not only elevates the levels of γ-aminobutyric acid, but also decreases the elevated levels of glutamate in CSF, which may also be important to the antiepileptic efficacy of vigabatrin. Patients with low CSF glutamate levels did not benefit from vigabatrin-induced changes in amino acid levels and successful monotherapy with carbamazepine did not affect CSF amino acid levels. The elevation of γ-aminobutyric acid is thus not the only way to achieve seizure control and there are several factors underlying the generation and control of seizures. Follow-up of the patients with high baseline glutamate CSF levels will show if the observed abnormalities are related to the severity of epilepsy in individual patients and if early treatment with vigabatrin of these patients could prevent the development of intractable epilepsy.