[Protective effects of Ginkgo Terpene Lactones Meglumine Injection on focal cerebral ischemia in rats].

To investigate the protective effects of ginkgo diterpene lactone meglumine injection (GDLMI) on cerebral focal ischemia reperfusion injury induced by middle cerebral artery occlusion (MCAO) in rats, and explore its possible mechanism. One hundred and forty male SD rats were randomly divided into sham operation group, model group, ginkgo biloba extract injection (Ginaton, 1.0 mL•kg⁻¹) group, nimodipine (0.4 mg•kg⁻¹) group, and GDLMI (5.2, 2.6, 1.3 mg•kg⁻¹) groups; All of rats received corresponding drugs by tail vein injection 4 days before operation (normal saline in model group and sham operation group). Except the sham operation group, the cerebral ischemic stroke model was established by MCAO method in right brain of the other rats. After 3 h of ischemia, all the animals received intravenous administration again. The neurobehavioral scores of rats after ischemia-reperfusion were evaluated and the infarct rate of brain tissue was observed by TTC staining. The super oxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA) and lactic acid (LA) contents in brain tissue homogenate and the concentration of Ca2+, glutamate (Glu) and aspartate (Asp), creatine phosphate kinase (CK-BB) and lactate dehydrogenase (LDH) content changes in cerebrospinal fluid were measured. As compared with the sham operation group, the cerebral infarction rate was increased significantly in the model group; the content of MDA and LA in the homogenate of brain tissue was increased, and the content of GSH and SOD was decreased; in cerebrospinal fluid, Ca2+ concentration was decreased, and the content of Glu and Asp, CK-BB and LDH increased significantly. As compared with the model group, the high and medium dose GDLMI groups can significantly reduce the cerebral infarction rate and improve the symptoms of neurological impairment; increase SOD and GSH activity, reduce MDA and LA content in serum; increase Ca2+ concentration in cerebrospinal fluid and decrease the content of neurotransmitter Glu and Asp as well as CK-BB and LDH. GDLMI could obviously improve neurologic impairment in model rats, and the mechanism may be related to recovering the blood brain barrier, scavenging free radicals, decreasing free Ca2+ inflow into the cells and the content of excitatory amino acid in cerebrospinal fluid to improve its protective effect on cerebral ischemia.

Effect of Gua Lou Gui Zhi decoction on focal cerebral ischemia-reperfusion injury through regulating the expression of excitatory amino acids and their receptors.

Gua Lou Gui Zhi decotion (GLGZD) has been reported to be an effective treatment for post­apoplectic limb spasm in the clinic. The present study aimed to investigate whether GLGZD had an affect on cerebral injuries induced by middle cerebral artery occlusion (MCAO) in rats and its possible mechanism. High­performance liquid chromatography was performed to analyze GLGZD. Furthermore, a model was established to assess the efficacy of GLGZD. Neurological defect scores and screen tests were analyzed. Brain ischemic infarct volume was measured using 2,3,5­triphenyl tetrazolium chloride staining and glutamic acid (Glu), aspartic acid (Asp) and glycine (Gly) levels in the cerebrospinal fluid were measured using the Hitachi automatic amino acid analyzer. Immunohistochemistry was performed to determine the expression of the α­amino­3­hydroxy­5­methyl­4­isoxazole­propionic acid (AMPA) and N­methyl­D­aspartic acid (NMDA) glutamate receptors, and to analyze histopathological change. GLGZD was found to improve neurological performance and reduce infarct volumes in MCAO rats. In addition, GLGZD was observed to enhance motor performance, which was assessed using the screen test. Furthermore, GLGZD was found to reduce Glu, Asp and Gly levels in the cerebrospinal fluid and downregulate the protein expression of the AMPA and NMDA glutamate receptors. Thus, it was demonstrated that GLGZD may exert neuroprotective effects through the modulation of excitatory amino acids, and AMPA and NMDA receptor expression.

Gua Lou Gui Zhi decoction exerts neuroprotective effects on post-stroke spasticity via the modulation of glutamate levels and AMPA receptor expression.

Spasticity is one of the most physically debilitating disabilities following stroke and may slow down the potential success of rehabilitation. Glutamate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been shown to play a crucial role in spasticity following cerebral ischemia/reperfusion (I/R) injury. Gua Lou Gui Zhi decoction (GLGZD) is a well-known traditional Chinese formula that has long been used clinically in China to treat muscular spasticity following stroke, epilepsy or spinal cord injury. However, the precise mechanisms behind its neuroprotective and anti-spasticity effects remain poorly understood. In the present study, using a rat model of focal cerebral I/R injury, we evaluated the neuroprotective and anti-spasticity effects of GLGZD and investigated the underlying mechanisms. We found that GLGZD improved neurological deficits and reduced infarct volumes in cerebral I/R-injured rats. In addition, GLGZD reduced cerebral ischemic spasticity since it improved the screen test and Hoffman's reflex (H-reflex) scores. It also reduced glutamate levels in the cerebrospinal fluid and altered the expression of the AMPA receptor subunits. Our data demonstrate that GLGZD exerts neuroprotective and anti-spasticity effects in a cerebral ischemia model via the modulation of glutamate levels and AMPA receptor expression.

Neuroprotective effect of Buyang Huanwu decoction against focal cerebral ischemia/reperfusion injury in rats--time window and mechanism.

ETHNOPHARMACOLOGICAL RELEVANCE: Buyang Huanwu Decoction, a traditional Chinese medicine, consists of different herbal medicines, and has been traditionally used for centuries to treat paralysis and stroke. However, its optimal therapeutic time window and the mechanism are still unclear. AIM OF THE STUDY: This study was designed to explore the therapeutic time window and mechanism of Buyang Huanwu Decoction on transient focal cerebral ischemia/reperfusion injury. MATERIALS AND METHODS: Middle cerebral artery occlusion was conducted in male Sprague-Dawley rats, and 40g/kg of Buyang Huanwu Decoction was intragastrically infused at different time points, and the same dose was infused every 24h for 3 days. The level of glutamate in cerebrospinal fluid and the expression of metabotropic glutamate receptor-1 RNA in striatum were detected before, during, and after ischemia/reperfusion. Neurological deficit scores and brain infarction volumes were measured at 72h after reperfusion. RESULT: Cerebral ischemia/reperfusion resulted in significant neurological deficit and extensive cerebral infarct volume, associated with a large amount of glutamate in cerebrospinal fluid and elevation of metabotropic glutamate receptor-1 RNA expression. Buyang Huanwu Decoction significantly suppressed the release of glutamate, and reduced the expression of metabotropic glutamate receptor-1 RNA. The neurological defect score and infarction volume were significantly improved by administration of Buyang Huanwu Decoction, when compared with the Ischemia group. CONCLUSIONS: Administration of Buyang Huanwu Decoction, within 4h of post-transient focal stroke, reduced significant cerebral ischemia/reperfusion damage. The neuroprotective mechanism of Buyang Huanwu Decoction is, in part, associated with the down-regulation of metabotropic glutamate receptor-1 RNA and inhibition of glutamate release resulting from cerebral ischemia.

Neuroprotective effect of curcumin in an experimental rat model of subarachnoid hemorrhage.

BACKGROUND: Subarachnoid hemorrhage (SAH) causes a high mortality rate and morbidity. It was suggested that oxidant stress plays an important role in neuronal injury after SAH. Therefore, we assessed the effect of curcumin on reducing cerebral vasospasm and neurologic injury in a SAH model in rat. METHODS: A double-hemorrhage model was used to induce SAH in rats. Groups of animals were treated with intraperitoneal injection of 20 mg/kg curcumin (curcumin group, n = 24) or dimethyl sulfoxide (vehicle group, n = 33), normal saline (SAH group, n = 34) or normal saline (sham group, n = 22), 3 h after SAH induction and daily for 6 days. Glutamate was measured before SAH induction and once daily for 7 days. Glutamate transporter-1, wall thickness and the perimeter of the basilar artery, neurologic scores, neuronal degeneration, malondialdehyde, superoxide dismutase, and catalase activities were assessed. RESULTS: Changes of glutamate levels were lower in the curcumin group versus the SAH and vehicle groups, especially on day 1 (56 folds attenuation vs. vehicle). Correspondingly, glutamate transporter-1 was preserved after SAH in curcumin-treated rats. In the hippocampus and the cortex, malondialdehyde was attenuated (30% and 50%, respectively). Superoxide dismutase (35% and 64%) and catalase (34% and 38%) activities were increased in the curcumin rats compared with the SAH rats. Mortality rate (relative risk: 0.59), wall thickness (30%) and perimeter (31%) of the basilar artery, neuron degeneration scores (39%), and neurologic scores (31%) were improved in curcumin-treated rats. CONCLUSIONS: Curcumin in multiple doses is effective against glutamate neurotoxicity and oxidative stress and improves the mortality rate in rats with SAH.

Synaptic properties of thalamic input to the subgranular layers of primary somatosensory and auditory cortices in the mouse.

The classification of synaptic inputs is an essential part of understanding brain circuitry. In the present study, we examined the synaptic properties of thalamic inputs to pyramidal neurons in layers 5a, 5b, and 6 of primary somatosensory (S1) and auditory (A1) cortices in mouse thalamocortical slices. Stimulation of the ventral posterior medial nucleus and the ventral division of the medial geniculate body resulted in three distinct response classes, two of which have never been described before in thalamocortical projections. Class 1A responses included synaptic depression and all-or-none responses, while Class 1B responses exhibited synaptic depression and graded responses. Class 1C responses are characterized by mixed facilitation and depression as well as graded responses. Activation of metabotropic glutamate receptors was not observed in any of the response classes. We conclude that Class 1 responses can be broken up into three distinct subclasses, and that thalamic inputs to the subgranular layers of cortex may combine with other, intracortical inputs to drive their postsynaptic target cells. We also integrate these results with our recent, analogous study of thalamocortical inputs to granular and supragranular layers (Viaene et al., 2011).

[Effect of polydatin on dynamic changes of excitatory amino acids in cerebrospinal fluid of cerebral hemorrhage rats].

OBJECTIVE: To observe the effects of polydatin on dynamic changes of excitatory amino acids in cerebrospinal fluid and water content of brain tissue of cerebral hemorrhage rats. And to discuss the therapeutic action and mechanisms of polydatin on brain hemorrhagic injured rats. METHOD: A quantitative determination method of Asp and Glu was established by microdialysis-HPLC. The cerebral hemorrhage model in rats was induced by local injection of type VII collagenase. The dynamic changes of Asp and Glu in cerebrospinal fluid were observed on 0, 6, 12, 24, 36, 48, 60, 72, 84, 96, 108 h of cerebral hemorrhage rats, and then the water content of brain tissue was detected. RESULT: The content of Asp and Glu increased rapidly within 24 h after cerebral hemorrhage, and to the highest in 24 h, then decreased gradually. Compared with the cerebral hemorrhage model group, the content of Asp and Glu increased slowly in polydatin group, and there were significant differences in 12-72 h and 6-84 h (P < 0.01, P < 0.05), but there was no significant difference after 84 h and 96 h. Compared with sham group, water content of brain tissue significantly higher in model group, while significantly lower (P < 0.01) in polydatin group. CONCLUSION: Polydatin can inhibit increasing content of Asp and Glu in cerebrospinal fluid dynamics, and significantly inhibit cerebral edema of cerebral hemorrhage rats. It shows that the mechanisms of anti-cerebral hemorrhage injury of polydatin may be related to increasing of excitatory amino acids after cerebral hemorrhage.

Anti-brain autoantibodies and altered excitatory neurotransmitters in obsessive-compulsive disorder.

Although serum autoantibodies directed against basal ganglia (BG) implicate autoimmunity in the pathogenesis of obsessive-compulsive disorder (OCD), it is unclear whether these antibodies can cross the blood-brain barrier to bind against BG or other components of the OCD circuit. It is also unclear how they might lead to hyperactivity in the OCD circuit. We examined this by investigating the presence of autoantibodies directed against the BG or thalamus in the serum as well as CSF of 23 OCD patients compared with 23 matched psychiatrically normal controls using western blot. We further investigated CSF amino acid (glutamate, GABA, taurine, and glycine) levels and also examined the extent to which these levels were related to the presence of autoantibodies. There was evidence of significantly more binding of CSF autoantibodies to homogenate of BG as well as to homogenate of thalamus among OCD patients compared with controls. There was no significant difference in binding between patient and control sera except for a trend toward more bands to BG and thalamic protein corresponding to 43 kD among OCD patients compared with controls. CSF glutamate and glycine levels were also significantly higher in OCD patients compared with controls, and further multivariate analysis of variance showed that CSF glycine levels were higher in those OCD patients who had autoantibodies compared with those without. The results of our study implicate autoimmune mechanisms in the pathogenesis of OCD and also provide preliminary evidence that autoantibodies against BG and thalamus may cause OCD by modulating excitatory neurotransmission.

Metabolic alterations in medication-free patients with bipolar disorder: a 3T CSF-corrected magnetic resonance spectroscopic imaging study.

The objective of this study was to determine whether cerebrospinal fluid(CSF)-corrected concentrations of N-acetylaspartate are lower in several brain regions of drug- and medication-free subjects with bipolar disorder as compared with matched healthy controls. Bipolar subjects (n=21) and age- and sex-matched healthy control (n=21) were studied using proton magnetic resonance spectroscopic imaging on a 3T magnetic resonance (MR) scanner. Spectra were quantified using the LCModel, and metabolite values were CSF-corrected to yield metabolite concentrations. Fourteen regions of interest and five metabolite concentrations in each subject were selected for statistical analysis. We found that bipolar subjects had significantly decreased N-acetylaspartate concentrations in both caudate heads and the left lentiform nucleus. Choline and creatine in the head of the right caudate were also significantly decreased in bipolar subjects. Significantly increased myo-inositol was found in the left caudate head in bipolar subjects. Bipolar subjects showed significantly decreased glutamate/glutamine concentrations in the frontal white matter bilaterally and in the right lentiform nucleus. No differences were found for other metabolites examined. These preliminary findings suggest decreased neuronal density or viability in the basal ganglia and neurometabolic abnormalities in the frontal lobes of subjects with bipolar disorder.

Intrathecal substance P (1-7) prevents morphine-evoked spontaneous pain behavior via spinal NMDA-NO cascade.

Previous research has shown that injection of high-dose of morphine into the spinal lumbar intrathecal (i.t.) space of rats elicits an excitatory behavioral syndrome indicative of severe vocalization and agitation. Substance P N-terminal fragments are known to inhibit nociceptive responses when injected i.t. into animals. In this study, we investigated the effect of i.t. substance P (1-7) on both the nociceptive response and the extracellular concentrations of glutamate and nitric oxide (NO) metabolites (nitrite/nitrate) evoked by high-dose i.t. morphine (500 nmol). The induced behavioral responses were attenuated dose-dependently by i.t. pretreatment with the substance P N-terminal fragment substance P (1-7) (100-400 pmol). The inhibitory effect of substance P (1-7) was reversed significantly by pretreatment with [d-Pro2, d-Phe7]substance P (1-7) (20 and 40 nmol), a d-isomer and antagonist of substance P (1-7). In vivo microdialysis analysis showed a significant elevation of extracellular glutamate and NO metabolites in the spinal cord after i.t. injection of high-dose morphine (500 nmol). Pretreatment with substance P (1-7) (400 pmol) produced a significant reduction on the elevated concentrations of glutamate and NO metabolites evoked by i.t. morphine. The reduced levels of glutamate and NO metabolites were significantly reversed by the substance P (1-7) antagonist (40 nmol). The present results suggest that i.t. substance P (1-7) may attenuate the excitatory behavior (vocalization and agitation) of high-dose i.t. morphine by inhibiting the presynaptic release of glutamate, and reducing NO production in the dorsal spinal cord.

[Spinal cord protection and opioids].

Opioids, when administered in large doses, were reported to produce brain damage primarily in limbic system and association areas in animals. We recently found the result that intrathecal (IT) morphine after a short interval of aortic occlusion in the rodent model induced transient spastic paraparesis via opioid receptor-coupled effects in the spinal cord. Histopathological analysis revealed the possibility that IT morphine could induce degeneration of spinal ventral neurons even after a short lasting of spinal cord ischaemia in rats, and this degeneration was associated with the activation of spinal N-methyl-D-aspartate receptors by elevation of glutamate release in cerebrospinal fluid after IT morphine. Therefore, we would like to emphasize that all anesthesiologists should be aware of the possibility of morphine-induced paraplegia after thoracic aortic surgery and that we should carefully select appropriate analgesic agents from the several available opioids for these patients.

A CSF and postmortem brain study of D-serine metabolic parameters in schizophrenia.

Clinical trials demonstrated that D-serine administration improves schizophrenia symptoms, raising the possibility that altered levels of endogenous D-serine may contribute to the N-methyl D-aspartate receptor hypofunction thought to play a role in the disease. We hypothesized that cerebro-spinal fluid (CSF) D-serine levels are decreased in the patients due to reduced synthesis and/or increased degradation in brain. We now monitored amino acid levels in CSF from 12 schizophrenia patients vs. 12 controls and in postmortem parietal-cortex from 15 control subjects and 15 each of schizophrenia, major-depression and bipolar patients. In addition, we monitored postmortem brain serine racemase and D-amino acid oxidase protein levels by Western-blot analysis. We found a 25% decrease in D-serine levels and D/L-serine ratio in CSF of schizophrenia patients, while parietal-cortex D-serine was unaltered. Levels of L-serine, L-glutamine and L-glutamate were unaffected. Frontal-cortex (39%) and hippocampal (21%) serine racemase protein levels and hippocampal serine racemase/D-amino acid oxidase ratio (34%) were reduced. Hippocampal D-amino-acid-oxidase protein levels significantly correlated with duration of illness (r=0.6, p=0.019) but not age. D-amino acid oxidase levels in patients with DOI>20 years were 77% significantly higher than in the other patients and controls. Our results suggest that reduced brain serine racemase and elevated D-amino acid oxidase protein levels may contribute to the lower CSF D-serine levels in schizophrenia.

Hypolocomotion in rats with chronic liver failure is due to increased glutamate and activation of metabotropic glutamate receptors in substantia nigra.

BACKGROUND/AIMS: Patients with hepatic encephalopathy show altered motor function, psychomotor slowing and hypokinesia. The underlying mechanisms remain unclear. This work's aims were: (1) to analyse in rats with chronic liver failure due to portacaval shunt (PCS) the neurochemical alterations in the basal ganglia-thalamus-cortex circuits; (2) to correlate these alterations with those in motor function and (3) to normalize motor activity of PCS rats by pharmacological means. METHODS: Extracellular neurotransmitters levels were analysed by in vivo brain microdialysis. Motor activity was determined by counting crossings in open field. RESULTS: Extracellular glutamate is increased in substantia nigra pars reticulata (SNr) of PCS rats. Blocking metabotropic receptor 1 (mGluR1) in SNr normalizes motor activity in PCS rats. In ventro-medial thalamus of PCS rats GABA is increased and it is normalized by blocking mGluR1 in SNr. Blocking mGluR1 in SNr increases and mGluR1 activation reduces glutamate in motor cortex and motor activity. CONCLUSIONS: Increased extracellular glutamate and activation of mGluR1 in SNr are responsible for reduced motor activity in rats with chronic liver failure. Blocking mGluR1 in SNr normalizes motor activity in PCS rats, suggesting that, under appropriate conditions, similar treatments could be useful to treat the psychomotor slowing and hypokinesia in patients with hepatic encephalopathy.

Effects of MK-801 (dizocilpine) on brain cell membrane function and energy metabolism in experimental Escherichia coli meningitis in the newborn piglet.

We evaluated the efficacy of non-competitive N-methyl-D-aspartate receptor antagonist MK-801 (dizocilpine) as an adjuvant therapy in experimental neonal bacterial meningitis. Meningitis was induced by injecting 10(6) colony forming units of Escherichia coli into the cisterna magna. MK-801 3 mg/kg was given as a bolus intravenous injection, 30 min before the induction of meningitis. MK-801 did not down-modulate the inflammatory parameters, such as increased intracranial pressure, cerebrospinal fluid (CSF) leukocytosis, increased lactate and TNF-alpha levels in the CSF, and hypoglycorrhachia observed in the meningitis group. MK-801 did not significantly attenuate the elevated glutamate concentration in the CSF. However, MK-801 showed some neuroprotective effects as evidenced by significant attenuation of cerebral lipid peroxidation products (conjugated dienes) and increase of brain high-energy phosphate compounds (ATP and PCr). Improvement in cerebral cortical cell membrane Na+, K+ -ATPase activity did not reach a statistical significance. These results suggest that MK-801 was effective in ameliorating brain injury in neonatal bacterial meningitis, although it failed to attenuate the inflammatory responses.

Effects of MK-801 (dizocilpine) on Brain Cell Membrane Function and Energy Metabolism in Experimental Escherichia coli Meningitis in the Newborn Piglet

We evaluated the efficacy of non-competitive N-methyl-D-aspartate receptor antagonist MK-801 (dizocilpine) as an adjuvant therapy in experimental neonal bacterial meningitis. Meningitis was induced by injecting 10(6) colony forming units of Escherichia coli into the cisterna magna. MK-801 3 mg/kg was given as a bolus intravenous injection, 30 min before the induction of meningitis. MK-801 did not down-modulate the inflammatory parameters, such as increased intracranial pressure, cerebrospinal fluid (CSF) leukocytosis, increased lactate and TNF-alpha levels in the CSF, and hypoglycorrhachia observed in the meningitis group. MK-801 did not significantly attenuate the elevated glutamate concentration in the CSF. However, MK-801 showed some neuroprotective effects as evidenced by significant attenuation of cerebral lipid peroxidation products (conjugated dienes) and increase of brain high-energy phosphate compounds (ATP and PCr). Improvement in cerebral cortical cell membrane Na+, K+ -ATPase activity did not reach a statistical significance. These results suggest that MK-801 was effective in ameliorating brain injury in neonatal bacterial meningitis, although it failed to attenuate the inflammatory responses.

Antischizophrenic activity independent of dopamine D2 blockade.

Currently, the drug therapy of schizophrenia consists of blockade of central dopamine D2 receptors. There is, however, an urgent medical need for alternative, more effective treatments. Clinical and preclinical literature suggests that stimulation of AMPA-type glutamate receptors may be involved in positive symptoms of schizophrenia, whereas hypofunctionality of NMDA-type glutamate receptors may be involved in negative symptoms and cognitive deficits. Several pharmacological approaches are conceivable to prevent stimulation of AMPA receptors (AMPA receptor blockade, metabotropic glutamate receptors (mGlu(2) receptor) stimulation or lamotrigine-like Na(+)/Ca(2+) channel blockade). Similarly, several pharmacological principles are conceivable to enhance neurotransmission at NMDA receptors (catechol-o-methyl transferase inhibition, glycine uptake blockade, glutathione suppletion and others). In this review, the possible pharmacological approaches and their respective advantages and disadvantages are discussed.

Early expression of glutamate transporter proteins in ramified microglia after controlled cortical impact injury in the rat.

Traumatic brain injury is followed by increased extracellular glutamate concentration. Uptake of glutamate is mainly mediated by the glial glutamate transporters GLAST and GLT-1. Extent and distribution of GLAST and GLT-1 were studied in a rat model of controlled cortical impact injury (CCII). Western Blot analysis revealed lowest levels of GLAST and GLT-1 with a decrease by 40%-54% and 42%-49% between 24 and 72 h posttrauma. By 8 h after CCII, CSF glutamate levels were increased (10.5 microM vs. 2.56 microM in controls; P < 0.001), reaching maximum values by 48 h. A significant increase in de novo GLAST and GLT-1 expressing ramified microglia was observed within 4 h, reached a stable level by 48 h, and remained high up to 72 h after CCII. Furthermore, ramified microglia de novo expressed the neuronal glutamate transporter EAAC1 after CCII. Following CCII, GLAST/GLT-1 and GFAP coexpressing astrocytes were immediately reduced, reaching minimum levels within 8 h. This reduction of expression could be either due to protein downregulation or loss of astrocytes. At 72 h, a marked population of GLAST- and GLT-1-positive reactive astrocytes appeared. These results support the hypothesis that reduced astrocytic GLAST and GLT-1 protein levels following CCII contribute to evolving secondary injury. Microglia are capable of de novo expressing glutamate transporter proteins, indicating that the expression of glial and neuronal glutamate transporters is not restricted to a specific glial or neuronal lineage. Ramified microglia may play an important compensatory role in the early regulation of extracellular glutamate after CCII.

CSF glutamate/GABA concentrations in pyridoxine-dependent seizures: etiology of pyridoxine-dependent seizures and the mechanisms of pyridoxine action in seizure control.

Several lines of evidence suggest that the binding affinity of glutamate decarboxylase (GAD) to the active form of pyridoxine is low in cases of pyridoxine-dependent seizures (PDS) and that a quantitative imbalance between excitatory (i.e. glutamate) and inhibitory (i.e. gamma-aminobutyric acid, GABA) neurotransmitters could cause refractory seizures. However, inconsistent findings with GAD insufficiency have been reported in PDS. We report a case of PDS that is not accompanied by an elevated cerebrospinal fluid (CSF) glutamate concentration. Intravenous pyridoxine phosphate terminated generalized seizures which were otherwise refractory to conventional anti-epileptic medicines. No seizure occurred once oral pyridoxine (13.5 mg/kg per day) was started in combination with phenobarbital sodium (PB, 3.7 mg/kg per day). The electroencephalogram (EEG) normalized approximately 8 months after pyridoxine was started. The patient is gradually acquiring developmental milestones during the 15 months follow-up period. The CSF glutamate and GABA concentrations were determined on three separate occasions: (1) during status epilepticus; (2) during a seizure-free period with administration of pyridoxine and PB; and (3) 6 days after suspension of pyridoxine and PB and immediately before a convulsion. The CSF glutamate level was below the sensitivity of detection (<1.0 microM) on each of the three occasions; the CSF GABA level was within the normal range or moderately elevated. The CSF and serum concentrations of vitamin B6-related substances, before pyridoxine supplementation, were within the normal range. We suggest that (1) PDS is not a discrete disease of single etiology in that insufficient activation of GAD may not account for seizure susceptibility in all cases and (2) mechanism(s) of anti-convulsive effect of pyridoxine, at least in some cases, may be independent of GAD activation.

Heat-stress-induced hyperthermia alters CSF osmolality and composition in conscious rabbits.

Amino acids have received increased attention with regard to their thermoregulatory effects and possible role as neurotransmitters within the thermoregulatory system. The purpose of the present work was to evaluate in conscious rabbits the changes in cerebrospinal fluid (CSF) concentration of taurine, GABA, aspartate, and glutamate during exposure to high ambient temperature (50 min, 40 degrees C) to investigate their involvement in heat stress (HS). CSF and plasma osmolality and CSF concentrations of some cations and proteins were also determined. HS animals underwent transient hyperthermia and thereafter fully recovered. This was accompanied by a significant rise in CSF and plasma osmolality, CSF protein, calcium, taurine, and GABA. Artificial CSF osmolality measurements after addition of CaCl(2) or taurine demonstrated that the increased CSF osmolality after HS is accounted for, only in part, by the increased concentrations of either calcium and taurine. It is suggested that, during HS, taurine and GABA are released in the extracellular space of brain tissues in higher amounts, possibly to counteract the resulting hyperthermia.

Nerve growth factor inducer, 4-methyl catechol, potentiates central sensitization associated with acceleration of spinal glutamate release after mustard oil paw injection in rats.

1. In rats, injection of mustard oil (MO) into the paw caused a gradual increase in flinching of the injected paw and this algogenic behavior corresponded with an increase in the CSF-Glu level. 2. The nerve growth factor (NGF) inducer, 4-methyl catechol (4MC), enhanced the frequency of flinching and this effect was dose dependent. In addition, spinal CSF-Glu release was significantly above baseline 10 min after MO injection. In contrast, morphine (MOR) pretreatment completely blocked this behavioral and neurohumoral effect. 3. Anti-NGF paw injection attenuated the algogenic behavior and spinal Glu release otherwise observed after 4MC treatment. 4. The results demonstrated that MO-induced hyperalgesia is associated with increased CSF-Glu release and that this effect is potentiated by a NGF inducer. These data also suggest a possible involvement of NGF in the development of central sensitization after acute peripheral nociceptive stimulation.