Amino acid neurotransmitter alterations in three sublines of Rb mice differing by their susceptibility to audiogenic seizures

The levels of inhibitory amino acids (Tau, Gly), or excitatory amino acids (Glu, Asp) and Gln, precursor of GABA, have been determined, under resting conditions, in 17 brain areas of 3 sublines of inbred Rb mice displaying different responses to an acoustic stimulus. Rb1 mice were clonictonic seizure-prone, Rb2 mice were clonic seizure-prone and Rb3 mice were seizure resistant. Profile of distribution in the brain of each one of these amino acids differed. Maximum to minimum level ratio was higher for Tau (3.8) than for Glu or Asp or Gln (2). The level of Gly was similar in 13 out of the 17 areas examined. Multiple inter-subline differences were recorded for each amino acid. These differences have been analyzed considering the seizure susceptibility or severity of the three Rb sublines. Common lower levels (approximately –20%: Rb1/Rb3, Rb2/Rb3) of Gln in Temporal Cortex may be implicated in seizure susceptibility. Seirure severity (Rb1/Rb2) seems to correlate, in some areas, with additional lower amounts of GABA already reported and, to a lower extent, of Asp (–19% in striatum, inferior colliculus and cerebellum), of Tau and Gly; a tendency for a rise in Gln content was observed in certain others (10–20% in olfactory bulb, thalamus, hypothalamus, substantia nigra, and frontal, temporal and occipital cortex). The data and correlations recorded provide guidelines for further investigations for synaptosomal and metabolic alterations in the three sublines of the same strain of Rb mice.Abbreviations used GABA 4-aminobutyrate - Tau taurine - Gly glycine - Asp aspartate - Glu glutamate - Gln glutamine - GEPR genetically epilepsy-prone rat - OB olfactory bulbs - OT olfactory tubercles - Sr striatum - Se septum - Hy hypothalamus - Hi hippocampus - Th thalamus - A amygdala - SC superior colliculus - IC interior colliculus - SN substantia nigra - FCx frontal cortex - TCx temporal cortex - OCx occipital cortex - C cerebellum - P pons - Ra raphe     

Involvement of synaptosomal neurotransmitter amino acids in audiogenic seizure-susceptibility and-severity of Rb mice

The involvement of synaptosomal neurotransmitter amino-acids in seizure susceptibility and seizure severity was explored. The amino-acid contents of brain synaptosomes were determined in three sublines of Rb mice differing in their response to an acoustic stimulus: Rb1, clonic-tonic seizure-prone, Rb2, clonic seizure-prone, and Rb3, seizure-resistant. Synaptosomes were prepared from 6 brain areas considered to be involved in seizure activity: olfactory bulbs, amygdala, inferior colliculus, hippocampus, cerebellum, pons-medulla. The steady-state levels of GABA and glycine (Gly), inhibitory amino-acids, of taurine (Tau), an inhibitory neurotransmitter of neuromodulator, of aspartate (Asp) and glutamate (Glu), excitatory amino-acids, as well as of serine (Ser) and glutamine (Gln), two precursors of neurotransmitter amino-acids, were determined by HPLC. Low levels of Tau, GABA, and Ser in hippocampus, Gly in amygdala, Glu in hippocampus, inferior colliculus and pons, Gln and Asp in inferior colliculus appeared to correlate with seizure-susceptibility. GABA and Asp in olfactory bulb, Gln in amygdala, hippocampus and pons, ser in olfactory bulb and pons, appeared to be associated either with seizure-severity or-diversity. A strong involvement of hippocampus (Tau, GABA, Ser, Glu, and Gln) and inferior colliculus (Asp, Glu, Gln) in audiogenic seizure-susceptibility, and of olfactory bulb (GABA, Asp) in seizure-severity and/or-diversity is suggested.Special issue dedicated to Dr. Alan N. Davison.     

Time-Related Cortical Amino Acid Changes After Basal Forebrain Lesion: A Microdialysis Study

Abstract: Cholinergic basal forebrain (BF) lesions in experimental animals have been used as a potential model for cholinergic deficits in cortex and hippocampus that occur in normal aging and Alzheimer's disease (AD). Glutamatergic cortical neurons are also affected in AD and could be part of the neurodegenerative process. In the present study, the effect of bilateral BF lesion with ibotenic acid microinjection on cortical extracellular amino acid levels was determined. Samples were collected every 20 min with microdialysis probes in awake, freely moving rats under basal and potassium stimulation conditions and measured by HPLC with fluorescence detection. Microdialysis experiments were performed 13 days, 21 days, and 30 days after BF lesion. The effectiveness of the lesion was shown by a significant 30% depletion in acetyl-CoA:choline O -acetyltransferase (EC 2.3.1.6) activity in the frontal cortex. Under basal conditions at 13 days only extracellular levels of taurine (Tau) and Glu were significantly reduced. Tau and Glu levels were recovered after 21 days and 30 days, respectively. In contrast, increase in Gly levels reaches its significance only at 30 days after lesion. Significant increases of Gln levels were observed at 21 days and 30 days. Asp and Ser levels remained constant throughout the period studied. Potassium stimulation led to increased Asp, Glu, Gly, and Tau levels, whereas Gln content decreased and Ser remained unaltered. As Ser is not believed to be a neurotransmitter, its lack of variation in any of the experimental conditions studied supports specific neuronal changes of the other amino acids. Results are discussed with reference to data observed in AD patients and possible mechanisms underlying the changes are suggested.     

Effects of Prostaglandin E2 and Capsaicin on Behavior and Cerebrospinal Fluid Amino Acid Concentrations of Unanesthetized Rats: A Microdialysis Study

Abstract: Prostaglandin E₂ (PGE₂) delivered to the spinal cord produces an increased sensitivity to noxious (hyperalgesia) and innocuous (allodynia) stimuli. The mechanisms that underlie this effect remain unknown, but a PGE₂-evoked enhancement of spinal neurotransmitter release may be involved. To address this hypothesis, we examined the effect of PGE₂ on CSF concentrations of amino acids and also the modulatory effect of PGE₂ on capsaicin-evoked changes of spinal amino acid concentrations using a microdialysis probe placed in the lumbar subarachnoid space. Amino acids were quantified using HPLC with fluorescence detection. Addition of 1 mM, but not 10 or 100 µM, PGE₂ to the perfusate for a 10-min period (flow rate, 5 µl/min) evoked an immediate increase (80–100%) in glutamate (Glu), aspartate (Asp), taurine (Tau), glycine (Gly), and γ-aminobutyric acid (GABA) concentrations. Similarly, capsaicin infusion (0.1–10 µM) induced a dose-dependent increase in Glu, Asp, Tau, Gly, GABA, and ethanolamine levels. Significant increases in amino acid levels evoked by PGE₂ or capsaicin were associated with a touch-evoked allodynia. The combination of PGE₂ (10 µM) and capsaicin (0.1 or 1.0 µM) at concentrations that individually had no effect together evoked a significant increase (60–100%) in Glu, Asp, Tau, Gly, and GABA concentrations and produced tactile allodynia. These data demonstrate that spinally delivered PGE₂ or capsaicin substantially elevates CSF concentrations of both excitatory and inhibitory amino acids. The capacity of PGE₂ to enhance and prolong capsaicin-evoked amino acid concentrations may be one of the mechanisms by which spinal PGE₂ produces hyperalgesia and allodynia.     

衰老对大鼠脑区氨基酸水平的影响

本文测定了正常青龄组（３月龄）和老龄组（２０月龄）大鼠不同脑区（皮层、小脑海马、纹状体和下丘脑）谷氨酸、天门冬氨酸、甘氨酸、ｒ－氨基丁酸和牛磺酸的含量。结果表明：在衰老过程中大鼠某些脑区谷氨酸、天门冬氨酸、甘氨酸和牛磺酸水平显著降低;而纹状体γ－氨基丁酸含量则显著升高。     

Changes in free amino acid concentrations in serum,brain, and CSF throughout embryogenesis

Using the developing chick embryo as a model and a very sensitive micromethod for amino acid analysis, a complete analysis is presented of the developmental changes in free amino acid concentration in the blood, in the CSF, and in two different brain regions (optic lobe and frontal lobe) of the chick embryo (from day 4 of incubation, until day 5 post hatching). The developmental profile of Lys is the only one that is almost identical in all three compartments. The developmental profiles of the serum and of the brain are very similar for Arg and Phe, less so for Leu and Gly, and towards the end of the embryonic period, similar also for Val, Ile, Trp, and Met. The amino acid concentrations in the CSF are either much lower than in serum and brain already at the earliest stages, or they progressively decline to levels lower than those in brain and serum, most rapidly between day 6 and 8 of embryonic life. The concentrations of neuroactive amino acids (Gln, Glu, Asp, GABA, Tau, and Gly) in both brain regions begin to increase very early, and continue to rise, except Tau, which goes through a maximum at day 8. Comparative analysis of the developmental profiles of each amino acid in serum, brain, and CSF reveals that the blood supply and the cellular uptake, retention, and metabolism by neural cells are the major determinants of the free amino acid pool of the developing brain.     

Severity of experimental traumatic brain injury modulates changes in concentrations of cerebral free amino acids

In this study, concentrations of free amino acids (FAA) and amino group containing compounds (AGCC) following graded diffuse traumatic brain injury (mild TBI, mTBI; severe TBI, sTBI) were evaluated. After 6, 12, 24, 48 and 120 hr aspartate (Asp), glutamate (Glu), asparagine (Asn), serine (Ser), glutamine (Gln), histidine (His), glycine (Gly), threonine (Thr), citrulline (Cit), arginine (Arg), alanine (Ala), taurine (Tau), γ‐aminobutyrate (GABA), tyrosine (Tyr), S‐adenosylhomocysteine (SAH), l ‐cystathionine (l ‐Cystat), valine (Val), methionine (Met), tryptophane (Trp), phenylalanine (Phe), isoleucine (Ile), leucine (Leu), ornithine (Orn), lysine (Lys), plus N‐acetylaspartate (NAA) were determined in whole brain extracts (n = 6 rats at each time for both TBI levels). Sham‐operated animals (n = 6) were used as controls. Results demonstrated that mTBI caused modest, transient changes in NAA, Asp, GABA, Gly, Arg. Following sTBI, animals showed profound, long‐lasting modifications of Glu, Gln, NAA, Asp, GABA, Ser, Gly, Ala, Arg, Citr, Tau, Met, SAH, l ‐Cystat, Tyr and Phe. Increase in Glu and Gln, depletion of NAA and Asp increase, suggested a link between NAA hydrolysis and excitotoxicity after sTBI. Additionally, sTBI rats showed net imbalances of the Glu‐Gln/GABA cycle between neurons and astrocytes, and of the methyl‐cycle (demonstrated by decrease in Met, and increase in SAH and l ‐Cystat), throughout the post‐injury period. Besides evidencing new potential targets for novel pharmacological treatments, these results suggest that the force acting on the brain tissue at the time of the impact is the main determinant of the reactions ignited and involving amino acid metabolism.     

Regional concentrations of transmitter amino acids after spinal cord ischaemia in the rabbit

Concentrations of Asp, Glu, Gly, GABA and Gln were studied in the ventral and dorsal horns of the rabbit spinal cord after ligation of the abdominal aorta. The most significant changes observed after 10, 20 and 40 min ischaemia were an increase in the Asp and GABA concentration in the ventral horns and an increase in the Asp, Gly and GABA concentration in the dorsal horns. These changes correspond to shifts in the relevant reactions under conditions of the altered redox equilibrium in the tissue during ischaemia. Four days after 10 min ischaemia, amino acid concentrations in the spinal cord were at the control levels. Four days after 20 and 40 min ischaemia Asp, Gly and GABA concentrations were decreased in the ventral horns and Asp, Gly, GABA and Glu concentrations in the dorsal horns. The percentually greater decrease in the concentration in the ventral horns may be associated with the greater morphological damage to these structures.     

Long lasting effects of audiogenic seizures on synaptosomal neurotransmitter amino acids in Rb mice

Long lasting alterations of synaptosomal amino acid neurotransmitters following a single or several audiogenic seizures and/or acoustic stimulations were investigated in six brain areas-olfactory bulbs (OB), amygdala (A), hippocampus (Hi), cerebellum (C), inferior colliculus (IC), ponsmedulla (P)- of three sublines of Rb mice: audiogenic seizure-prone Rb1 and Rb2, seizure-resistant Rb3. Changes in the synaptosomal levels of aspartate (Asp), glutamate (Glu), taurine (Tau), 4-amino butyrate (GABA), glycine (Gly) and some closely related precursors, serine (Ser) and glutamine (Gln), were recorded 15–18 hours after a single or multiple acoustic stimulations. Changes were more frequent, or larger, after polystimulation. Some alterations appeared to be attributable to an effect of the acoustic stress.In both seizure-prone sublines, after a single or repeated seizures, an increase in synaptosomal Asp was observed in IC. Decreases in Asp and Tau in OB and Ser in A, an increase in Gln in IC were only observed after repeated seizures, in Rb1 and Rb2 mice.Abbreviations used GABA 4-aminobutyrate - Tau taurine - Gly glycine - Ser serine - Asp aspartate - Glu glutamate - Gln glutamine - OB olfactory bulbs - A amygdala - Hi hippocampus - C cerebellum - IC interior colliculus - P pons Professeur Paul Mandel passed away on 6th October, 1992Special issue dedicated to Dr. Bernard W. Agranoff.     

Long-lasting effects of audiogenic seizures on neurotransmitter amino acids in Rb mice

The existence of long-lasting (15–18 h) alterations of neurotrasmitter amino acid levels following a single or repeated acoustic stimulations in audiogenic seizure-prone Rb1 and Rb2 mice and suizure-resistant Rb3 mice were investigated. The levels of glutamate, aspartate, glycine, taurine, and of some of their precursors: glutamine and serine were determined. Fourteen brain areas were examined. Alterations were found only in 6 brain areas (pons, olfactory bulbs, superior colliculus, inferior colliculus, olfactory tubercles and raphe). Most frequent occuring changes were observed in pons and olfactory tubercles. These changes concerned mainly the excitatory amino acids, glutamate, and aspartate. Alterations of taurine, glycine and serine were also recorded.Abbreviations GABA 4-aminobutyrate - Tau taurine - Gly glycine - Asp aspertate - Glu glutamate - Gln glutamine - Ser serine - OB olfactory bulbs - OT olfactory tubercles - Sr striatum - Se septum - Hy hypothalamus - Th thalamus - Hi hippocampus - A amygdala - SC superior colliculus - IC inferior colliculus - FC frontal cortex - C cerebellum - P pons medulla - Ra raphe - AA neurotransmitter amino acids - I inhibitory - E excitatory - SSL steady-state level Plesant memories of Lawrence Austin's sojourn in my group at Strasbourg gather upon me when I dedicate this article on this occasion for the contribution that Lawrence Austin has made for the cause of neurochemical researchers.     

Roles of glutamine in neurotransmission

Glutamine (Gln) is found abundantly in the central nervous system (CNS) where it participates in a variety of metabolic pathways. Its major role in the brain is that of a precursor of the neurotransmitter amino acids: the excitatory amino acids, glutamate (Glu) and aspartate (Asp), and the inhibitory amino acid, γ-amino butyric acid (GABA). The precursor-product relationship between Gln and Glu/GABA in the brain relates to the intercellular compartmentalization of the Gln/Glu(GABA) cycle (GGC). Gln is synthesized from Glu and ammonia in astrocytes, in a reaction catalyzed by Gln synthetase (GS), which, in the CNS, is almost exclusively located in astrocytes (Martinez-Hernandez et al., 1977). Newly synthesized Gln is transferred to neurons and hydrolyzed by phosphate-activated glutaminase (PAG) to give rise to Glu, a portion of which may be decarboxylated to GABA or transaminated to Asp. There is a rich body of evidence which indicates that a significant proportion of the Glu, Asp and GABA derived from Gln feed the synaptic, neurotransmitter pools of the amino acids. Depolarization-induced-, calcium- and PAG activity-dependent releases of Gln-derived Glu, GABA and Asp have been observed in CNS preparations in vitro and in the brain in situ. Immunocytochemical studies in brain slices have documented Gln transfer from astrocytes to neurons as well as the location of Gln-derived Glu, GABA and Asp in the synaptic terminals. Patch-clamp studies in brain slices and astrocyte/neuron co-cultures have provided functional evidence that uninterrupted Gln synthesis in astrocytes and its transport to neurons, as mediated by specific carriers, promotes glutamatergic and GABA-ergic transmission. Gln entry into the neuronal compartment is facilitated by its abundance in the extracellular spaces relative to other amino acids. Gln also appears to affect neurotransmission directly by interacting with the NMDA class of Glu receptors. Transmission may also be modulated by alterations in cell membrane polarity related to the electrogenic nature of Gln transport or to uncoupled ion conductances in the neuronal or glial cell membranes elicited by Gln transporters. In addition, Gln appears to modulate the synthesis of the gaseous messenger, nitric oxide (NO), by controlling the supply to the cells of its precursor, arginine. Disturbances of Gln metabolism and/or transport contribute to changes in Glu-ergic or GABA-ergic transmission associated with different pathological conditions of the brain, which are best recognized in epilepsy, hepatic encephalopathy and manganese encephalopathy.     

Cellular Origins of Endogenous Amino Acids Released into the Extracellular Fluid of the Rat Striatum During Severe Insulin-Induced Hypoglycemia

The effect of severe insulin-induced hypoglycemia on the extracellular levels of endogenous amino acids in the rat striatum was examined using the brain microdialysis technique. A characteristic pattern of alterations consisting of a 9-12-fold increase in aspartate (Asp), and more moderate increases in glutamate (Glu), taurine (Tau), and gamma-aminobutyric acid (GABA), was noted following cessation of electroencephalographic activity (isoelectricity). Glutamine (Gln) levels were reduced both during and after the isoelectric period and there was a delayed increase in extracellular phosphoethanolamine (PEA) content. The effects of decortication and excitotoxin lesions on the severe hypoglycemia-evoked efflux of endogenous amino acids in the striatum were also examined. Decortication reduced the release of Glu and Asp both 1 week and 1 month post-lesion. The efflux of other neuroactive amino acids was not affected significantly. In contrast, GABA, Tau, and PEA efflux was attenuated in kainate-lesioned striata. Glu and Asp release was also reduced under these conditions, and a smaller decrease in extracellular Gln was noted. These data suggest that GABA, Glu, and Asp are released primarily from their transmitter pools during severe hypoglycemia. The releasable pools of Tau and PEA appear to be located in kainate-sensitive striatal neurons. The significance of these results is discussed with regard to the excitotoxic theory of hypoglycemic cell death.     

Alterations in synaptosomal neurotransmitter amino acids in “petit-mal” rats at a daytime and a nighttime

The synaptosoma fractions of 6 brain areas-olfactory tubercles (OT), frontal cortex (FC), striatum (Sr), amygdala (A), thalamus (Th), hypothalamus (Hy)-have been analyzed for their neurotransmitter amino acids (AA) content in Wistar rats exhibiting petit-mal epilepsy (PM-E) and in controls (C). The analysis was carried out at 11 p.m. (nighttime corresponding to the acrophase for the hourly number of spike-wave complexes) and at 11 a.m. (daytime). A day versus night rhythmicity is recorded for synaptosomal inhibitory AA in control and in PM-E rats. However, day versus night variations are more frequent and more prominent in C rats than in PM-E rats. Two day versus night variations exist only in PM-E rats: increases of GABA level in Sr and of Asp in Hy. Differences between PME-and C in synaptosomal AA content are more likely to be present during the nighttime. During this period lower AA values for PM-E rats are found for one or several inhibitory AA in OT, Th, and FC. It seems that the differences between PM-E and C concerning the inhibitory AA correlate with the number of spike-wave discharges. Only in one brain area is there a similar difference for PM-E and C during daytime and nighttime: a decreased GABA content for PM-E rats in OT. The decrease is larger in nighttime than in daytime. This difference may serve as a marker for this epileptic disorder. Moreover, it is in OT that the greatest number of PM-E versus C differences in synaptosomal neurotransmitter AA are observed. In view of these and former data, the existence of different alterations in synaptosomal neurotransmitter AA for different types of epilepsy is suggested.Abbreviations used GABA 4-aminobutyrate - Tau taurine - Gly glycine - Asp aspartate - Glu glutamate - Gln glutamine - OT offactory tubereles - FC fronto-parietal cortex - Sr striatum - A amygdala - Th lateral thalamus - Hy lateral hypothalamus - AA neurotransmitter amino acids - I inhibitory - E excitatory - C control rats - PM-E petit-mal rats     

Somatostatin Potently Stimulates In Vivo Striatal Dopamine and γ-Aminobutyric Acid Release by a Glutamate-Dependent Action

Abstract: We have used in vivo microdialysis in anaesthetised rats to investigate whether somatostatin (SRIF) can play a neuromodulatory role in the striatum. When 100 n M SRIF was retrodialysed for 15 min, it increased concentrations of dopamine (DA) by 28-fold, γ-aminobutyric acid (GABA) by eightfold, and glutamate (Glu) by sixfold as well as those of aspartate (Asp) and taurine (Tau). These effects were both calcium- and tetrodotoxin-sensitive. Lower (10 or 50 n M ) and higher (1 µ M ) SRIF concentrations were less effective. Rapid sampling showed that whereas Asp and Glu concentrations were raised for 3 min at the start of 15-min SRIF infusions, those of DA were increased for 12 min. A second 15-min application of 100 n M SRIF given 135 min after the first application failed to increase transmitter release. An NMDA receptor antagonist, 2-amino-5-phosphonopentanoic acid (200 µ M ), blocked SRIF (100 n M )-evoked Asp, Glu, Tau, and GABA release and reduced that of DA. An α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate antagonist, 6,7-dinitroquinoxaline-2,3-dione (100 µ M ), blocked SRIF-induced DA and Tau release and reduced that of Asp, Glu, and GABA. These results show that SRIF increases DA, Glu, Asp, GABA, and Tau release in the rat striatum and suggest that its actions on DA and GABA release are mainly mediated through increased excitatory amino acid release.     

Microdialysis with High NaCl Causes Central Release of Amino Acids and Dopamine

Abstract: Recent studies have shown that the neuropeptides arginine-8-vasopressin (AVP) and oxytocin (OXT) are released within the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus in response to microdialysis of these nuclei with high-NaCl perfusion media. These results suggest an inherent osmosensitivity of SON and PVN neurons. To investigate whether the observed release of AVP/OXT is a unique phenomenon to these neuropeptides, several brain regions were examined for the release of amino acids or dopamine in response to high- or low-NaCl stimulation. Urethane-anesthetized male Sprague-Dawley rats were perfused with five-ion solution using U-shaped microdialysis probes. Samples were collected at 30-min intervals and analyzed for amino acids and dopamine by HPLC. In the dialysates of all perfusion areas, including the SON, PVN, hippocampus, and striatum, concentrations of Asp, Glu, Ser, Gln, Gly, taurine (Tau), and γ-aminobutyric acid (GABA) were significantly increased during perfusion with high-NaCl medium. This release was found to be dose dependent when tested in the hippocampus and striatum with perfusion medium containing 0.5 or 1.0 M NaCl. However, only the release of Glu and Ser was found to be Ca²⁺ dependent. In contrast, the use of mannitol, a nonionic osmolyte, for perfusions in the striatum in concentrations of 0.5 and 1 M resulted in reduced levels of amino acids in the dialysates (Glu, Ser, Gln, and Tau). Low-NaCl perfusion medium (0.01 M) resulted in significantly increased Glu, Tau, Gly, and GABA levels in the striatum. In addition, dopamine levels in striatal dialysates were significantly increased during stimulation with 1 M NaCl. These results indicate that stimulation with high NaCl concentrations affects the release of several neurotransmitters and is not specific for AVP and OXT. The described phenomenon of the release of amino acids in response to this stimulation seems to be a response to the changed ionic concentration rather than to the osmolality. In light of these findings shown for amino acids and dopamine as well as those previously reported for AVP, OXT, and angiotensin, it would appear that sensitivity to tonicity changes brought about by microdialysis may be a feature of many transmitter systems.     

Somatostatin and CCK-8 modulate release of striatal amino acids: role of dopamine receptors

The effects of somatostatin (SOM) and cholecystokinin octapeptide (CCK-8) on basal and potassium-evoked release of neurotransmitter amino acids were investigated in slices of rat caudate nucleus (CN) and, for comparison, cerebral cortex (CX). Endogenous aspartate (Asp), glutamate (Glu), glycine (Gly), and gamma-aminobutyric acid (GABA) were measured by high performance liquid chromatography. In both CN and CX, potassium (5-55 mM) produced a concentration-dependent increase in the release of Asp, Glu, Gly, and GABA in the presence of extracellular Ca2+. CCK-8 (1 microM) stimulated in CN the basal and K+-evoked release of Gly to 231% and 160% of control, respectively; this effect was blocked by sulpiride (SULP), a dopamine receptor antagonist. In contrast, SOM (1 microM) inhibited the K+-evoked release of Glu in CN by 26%, an effect that was not blocked by SULP. SOM and CCK-8 did not significantly affect the basal or K+ (35 mM)-evoked release of other amino acids in the CN or of any amino acids in CX. The results indicate that: CCK-8 facilitation of Gly release is dependent of Gly release is dependent on dopamine receptor activation, whereas the inhibition by SOM of Glu release is not: and the effects of SOM and CCK-8 are specific with respect to the brain region affected.     

Amino Acids in Rat Striatal Dialysates: Methodological Aspects and Changes After Electroconvulsive Shock

Extracellular levels of amino acids were estimated in dialysates of the rat striatum that were collected 1, 2, and/or more than 5 days after surgery, before (resting release) and during exposure to high K concentrations (50 mM) or electroconvulsive shocks. The resting release of several amino acids (Glu, Asn, Thr, Tau, Tyr, Gly, and Ala) was higher 9 days as compared to 1 day after surgery. In the 1-day preparation the resting release correlated highly with that observed with push-pull cannulas. The correlation with the tissue content of the amino acids was high only when they were divided into two groups (putative transmitters and metabolic intermediates). High K exposure produced increased output of Ala, ethanolamine (Eam), Asp, Glu, Tau, and Gly and a decrease in the egress of Gln 1 or 2 days after surgery. The effects on Asp and Glu had disappeared, and that on Gln reversed after 4-9 days. Electrically induced convulsions produced increased output of Ala, Gln, and Eam 1 or 2 days and 2 weeks after implantation of the probe. Changes were seen not only during but also (and some cases even more prominent) after the seizure. This study shows the usefulness of dialysis to monitor extracellular transmitter amino acids in the striatum of conscious rats (also bilateral dialysis was possible) for only a limited time after implantation of the probe. The dialysis method is suitable for longer time, when metabolic changes in amino acids are to be followed. In addition to transmitter release, glycolysis can be monitored by the measurement of Ala in the dialysate.     

Regional changes in the concentrations of glutamate,glycine, taurine,and GABA in the vitamin B-6 deficient developing rat brain: Association with neonatal seizures

It is well known that a dietary restriction of vitamin B-6 during gestation and lactation produces spontaneous seizures in neonatal animals. Since pyridoxal phosphate, one of the biologically active forms of vitamin B-6, is the cofactor for GAD the neonatal seizures have been attributed to low levels of brain GABA as a result of cofactor depletion. Although GABA levels are significantly lower in B-6 restricted neonatal rats with spontaneous seizures, seizure activity is not present in B-6 deficient adult rats or 28 day old rats in the present study, despite significantly low levels of brain GABA. These facts suggest that depletion of GABA is not the only biochemical alteration essential for the emergence of seizures. In the present study, the effect of vitamin B-6 undernutrition on the concentrations of the neuroactive amino acids, Glu, Gly, Tau, and GABA was determined in selected regions of the developing rat brain. The results show that the concentrations of Glu, Tau, and GABA were significantly lower and GLY significantly higher in selected brain regions of the B-6 restricted 14 day old rat compared to control tissue. Most of these changes were unique to 14 days of age, the time when spontaneous seizures are observed, and not present at 28 or 56 days of age when seizures are absent. This pattern of amino acid changes in the brain and the magnitude of the changes was consistent with those measured in a variety of chemically-induced animal models of epilepsy and in human epileptic foci. The regional distribution of amino acid changes was associated with brain regions which have been suggested to be responsible for the initiation and propagation of seizure activity. Two unique findings were also made in this study. First, there was a regional brain heterogeneity in the age-associated loss of brain Tau concentrations with the pons/medulla and substantia nigra appearing to be highly vulnerable and the hippocampus quite resistant to the loss of Tau. A second finding was the normalization of the neonatal GABA deficit in most brain regions by 56 days of age. The normalization of brain GABA was present in the face of continued dietary vitamin B-6 restriction. In summary, this study shows that the neuroactive amino acids Glu, Gly, Tau, and GABA are markedly altered in the seizure-prone vitamin B-6 restricted neonatal rat brain. The alterations in the brain concentration of Glu, Gly, and Tau may play an equally important role as GABA in the underlying mechanism of seizures associated with this condition.Abbreviations GAD Glutamic acid decarboxylase - GABA gamma-aminobutyric acid - Glu glutamate - Gly glycine - Tau taurine - CNS central nervous system - CTX cortex - HIPP hippocampus - C/P caudate/putamen - SN substantia nigra - Cb cerebellum - P/M pons/medulla     

LC-MS/MS检测癫痫患者神经递质类氨基酸

目的：建立液相色谱串联质谱同位素内标法检测神经递质类氨基酸并用于癫痫患者临床评价。方法：选用AAA-C18柱色谱柱,以乙腈水（含有0.01%七氟丁酸、0.1%甲酸）为流动相,采用梯度洗脱进行分离,血浆样品用iTRAQ-115衍生化试剂处理后,加入iTRAQ-114衍生化的氨基酸内标并进样,选用3200QTRAP型质谱仪的多重反应监测（MRM）扫描方式进行检测。疾病组与健康组的统计采用t检验和主成份分析。结果：疾病组和健康组氨基酸测定结果显示：Trp、GABA两组间没有显著性差异（P〉0.05）,Arg、Gly、Ser、Tau、Asp、Glu、EtN、两组间有显著性差异（P〈0.05）,通过PCA分析显示,疾病组与健康组之间差异明显,Asp、Glu、Ser等是引起差异的主要氨基酸。结论：试验方法灵敏、专属性强,并初步的用于癫痫患者体内氨基酸评价。     

Free amino acids in the spinal cord and ganglia of dogs after ligation of the abdominal aorta

The authors studied the effect of 40 min and 6 days occlusion of the abdominal aorta on the aspartate [Asp], glutamic acid [Glu], glutamine [Gln], glycine [Gly] and alanine [Ala] concentration in both parts of the grey matter of the lumbosacral cord, in the spinal ganglia and along the dorsal fasciculi. After 40 min ischaemia, an increase was found in the Glu, Gln, Gly and Ala concentration in the dorsal part of the grey matter and in the Glu, Gly and Ala concentration in the spinal ganglia. In the ventral part of the grey matter only the Ala concentration was increased. After 6-day ligation, the Asp and Gly concentration fell in the ventral horns, while the Gly concentration rose in the dorsal horns. The Ala and Asp concentration in the spinal ganglia rose. After this interval the Asp and Glu concentration also rose in the fasciculus gracilis. The Ala/Glu concentration ratio showed the most pronounced increase in the central horns of the grey matter.