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.     

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.     

Effects of dorsal root section and occlusion of dorsal spinal artery on the neurotransmitter candidates in rat spinal cord

In order to obtain further evidence of putative neurotransmitters in primary sensory neurons and interneurons in the dorsal spinal cord, we have studied the effects of unilateral section of dorsal roots and unilateral occlusion of the dorsal spinal artery on cholinergic enzyme activity and on selected amino acid levels in the spinal cord. One week after sectioning dorsal roots from caudal cervical (C₇) to cranial thoracic (T₂) levels, the specific activity of choline acetyltransferase (ChAT) was significantly decreased and acetylcholinesterase (AChE) showed a tendency to decrease in the dorsal quadrant on the operated side of the spinal cord. Dorsal root sectioning had little effect on the levels of free glutamic acid or other amino acids in the dorsal spinal cord. These results suggest that primary sensory neurons may include some cholinergic axons, and that levels of putative amino acid transmitters are not regulated by materials supplied by axonal transport from the dorsal root ganglia. By contrast, one week following unilateral occlusion of the dorsal spinal artery, the activities of ChAT and AChE were unchanged in the operated quadrant of the spinal cord, while decreases of Asp, Glu, and GABA, and an increase in Tau were detected. These findings are consistent with the proposals that such amino acids, but not ACh, may function as neurotransmitter candidates in interneurons of the dorsal spinal cord.Abbreviation used ACh acetylcholine - AChE acetylcholinesterase - Asp aspartic acid - ChAT choline acetyltransferase - GABA -aminobutyric acid - Glu glutamic acid - Gly glycine - SP substance P - Tau taurine     

Free amino acids in the spinal cord, ganglia and ischiadic nerve of the dog after ligature of the abdominal aorta

The effect of occlusion of the abdominal aorta for 10, 20 and 40 minutes on the concentration of aspartic and glutamic acids, glutamine, glycine, alanine and gamma-amino butyric acid in the anterior and posterior horns of the lumbosacral spinal cord was studied in the dog, further, concentration of amino acids (except GABA) in lumbosacral spinal ganglia and in the ischiadic nerve following 40 minutes of occlusion. The changes were most marked after 40 minutes of occlusion with a rise in concentration of alanine, glutamine and glutamic acid in the dorsal part of grey matter. Striking was also the simultaneous elevated concentration of Glu and Gln in spinal ganglia. The significance of these changes is discussed from the aspect of metabolism and function of nerve cells. Under physiological conditions the free amino acid pool in the central nervous system remains essentially constant. Under pathological conditions, however, like ischemic-hypoxic states, various changes occur.     

Distribution of glycine/GABA neurons in the ventromedial medulla with descending spinal projections and evidence for an ascending glycine/GABA projection

The ventromedial medulla (VM), subdivided in a rostral (RVM) and a caudal (CVM) part, has a powerful influence on the spinal cord. In this study, we have identified the distribution of glycine and GABA containing neurons in the VM with projections to the cervical spinal cord, the lumbar dorsal horn, and the lumbar ventral horn. For this purpose, we have combined retrograde tracing using fluorescent microspheres with fluorescent in situ hybridization (FISH) for glycine transporter 2 (GlyT2) and GAD67 mRNAs to identify glycinergic and/or GABAergic (Gly/GABA) neurons. Since the results obtained with FISH for GlyT2, GAD67, or GlyT2 + GAD67 mRNAs were not significantly different, we concluded that glycine and GABA coexisted in the various projection neurons. After injections in the cervical cord, we found that 29% ± 1 (SEM) of the retrogradely labeled neurons in the VM were Gly/GABA (RVM: 43%; CVM: 21%). After lumbar dorsal horn injections 31% ± 3 of the VM neurons were Gly/GABA (RVM: 45%; CVM: 12%), and after lumbar ventral horn injections 25% ± 2 were Gly/GABA (RVM: 35%; CVM: 17%). In addition, we have identified a novel ascending Gly/GABA pathway originating from neurons in the area around the central canal (CC) throughout the spinal cord and projecting to the RVM, emphasizing the interaction between the ventromedial medulla and the spinal cord. The present study has now firmly established that GABA and glycine are present in many VM neurons that project to the spinal cord. These neurons strongly influence spinal processing, most notably the inhibition of nociceptive transmission.     

Phospholipid Composition in Spinal Cord Regions after Ischemia/Reperfusion

Ischemia-reperfusion induced changes in concentration of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI) and sphingomyelin (SM) in the gray matter taken in toto, white matter, dorsal horns, intermediate zone and ventral horns of the rabbit's spinal cord were studied and compared with neurohistopathological changes. With the exception of PI concentration in the dorsal horns, ischemia of 25 min caused significant degradation of all phospholipids. While short-lasting recirculation (1 h) did not returned the levels of phospholipids to control values, postischemic recirculation for 3 h sharply increased the resynthesis of all phospholipids, but only the concentration of PE, PS, and PI in the dorsal horns and PC in the intermediate zone significantly improved and returned close to control values. Corresponding neurohistopathological changes resulting after the same reperfusion periods are given.     

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.     

Effect of unilateral motor cortex ablation on activity of choline acetyltransferase and levels of amino acid transmitter candidates in the spinal cord of adult monkeys

Evidence thatl-glutamate is a neurotransmitter of corticofugal fibers was sought by measuring changes in several biochemical markers of neurotransmitter function in discrete regions of spinal cord after ablation of sensorimotor cortex in monkeys. One and five weeks after unilateral cortical ablation, samples from six areas of spinal cord (ventral, lateral and dorsal regions of the left and right sides) were analysed for choline acetyltransferase (ChAT) activity and contents of amino acid transmitter candidates-glutamic acid (Glu), aspartic acid (Asp), glycine (Gly), taurine (Tau) and -aminobutyric acid (GABA). During one to five weeks after unilateral cortical ablation of the monkey, prolonged hemiplegia in the contralateral side was observed. Histological examination of the spinal cord 5 weeks after unilateral (left) cortical ablation showed no apparent change in either control (ipsilateral, left) or affected (contralateral, right) sides of the cord as examined by the Klüver-Barrera method. The ChAT activity as a cholinergic marker was scarcely changed in any region of either left (control) or right (affected) side of the spinal cord at one and five weeks after unilateral (left side) ablation of the motor cortex. Amino acid levels in each region of the spinal cord were not significantly changed one week after unilateral ablation of the motor cortex. However, a significant decrease of Glu content was observed in the lateral column of the affected (right) side compared to the control (left) side of cervical and lumbar cord five weeks after cortical ablation of the left motor area. No concomitant alterations of other amino acids were detected. These data strongly suggest thatl-Glu is a neurotransmitter for corticofugal pyramidal tract fibers to anterior horn secondary neurons related to motor control activity in monkey spinal cord.     

QUANTITATIVE HISTOCHEMISTRY OF γ-AMINOBUTYRIC ACID IN CAT SPINAL CORD WITH SPECIAL REFERENCE TO PRESYNAPTIC INHIBITION

Abstract— A method is described for quantifying the GABA distribution in cat spinal cord at 200–500 μn resolution. Isolated spinal cord (L5–S1) was frozen and sectioned at about 150 μm thickness. The frozen tissue section was cut into 200 or 500 μm square blocks. The GABA content of each square tissue block was determined by enzymic micromethods and GABA distribution was mapped quantitatively. Average GABA concentrations were: 0·4 mmol/l. in white matter, 1·2 mmol/l. in ventral horn and 1·7 mmol/l. in dorsal horn. The highest concentrations of GABA (2–3 mmol/l.) were found in the dorsolateral part of dorsal horn. In order to destroy the interneurons of dorsal horn, the blood vessels supplying the dorsal horn of the lumbar enlargement were unilaterally cauterized. Seven to 30 days after operation, both the size of dorsal root potential and the GABA level in the dorsal horn were markedly reduced on the cauterized side. These results suggest that GABA is highly concentrated in the interneurons of dorsal horn and functions as a transmitter of presynaptic inhibition.     

Presynaptic α2 Adrenoceptors Inhibit Glutamate Release from Rat Spinal Cord Synaptosomes

Abstract: The presynaptic regulation of amino acid release from nerve terminals was investigated using synaptosomes prepared from the rat spinal cord. The basal releases of endogenous glutamate (Glu), aspartate (Asp), and γ-amino-butyric acid (GABA) were 34.6, 21.5, and 10.0 pmol/min/mg of protein, respectively. Exposure to a depolarizing concentration of KCl (30 m M ) evoked 2.7-, 1.5-, and 2.9-fold increases in Glu, Asp, and GABA release, respectively. Clonidine reduced the K⁺-evoked overflow of Glu to 56% of the control overflow with a potency (IC₅₀) of 17 n M , but it did not affect K⁺-evoked overflow of Asp, GABA, and their basal releases. Similarly, noradrenaline inhibited the K⁺-evoked overflow of Glu, although phenylephrine and isoproterenol showed no effect. The inhibitory effect of clonidine was counteracted by α₂-adrenoceptor antagonists, rauwolscine, yohimbine, and idazoxan, regardless of the imidazoline structures. Because Glu is considered a neurotransmitter of primary afferents that transmit both nociceptive and nonnociceptive stimuli in the spinal cord, these data suggest that part of Glu release may be regulated by the noradrenergic system through α₂ adrenoceptors localized on the primary afferent terminals.     

Effect of chronic ethanol treatment and subsequent ischaemia on phospholipids and cholesterol in the rabbit spinal cord

Rabbits received ethanol p.o. (0.96 g. ml-1, 2.88 g.kg-1) for 30 days. Ischaemia was induced by abdominal aorta ligation for 40 min in animals with or without ethanol treatment. The content of total (TPL) and individual phospholipids, i.e. ethanolamine (PE), choline (PC), serine (PS), phospholipids and sphingomyelin (SM), as well as unesterified cholesterol (UC) was determined in the gracilis fascicle (Fg), and the dorsal (Dp) and ventral (Vp) part of the lumbar and cervical spinal cord. Chronic ethanol treatment resulted in a statistically significant decrease in the PE content in Dp of cervical spinal cord. Cholesterol content was increased in all parts of the spinal cord studied (increased UC/TPL molar ratio). Ischaemia of the spinal cord induced a significant decrease in PI. In ethanolic animals ischaemia decreased the PS content in Dp and Vp of ischaemized lumbar spinal cord. The combined effect of ischaemia and chronic ethanol did not result in a cumulative pattern of changes suggesting a partially opposite influence of both stimuli on lipid metabolism as well as its altered regulation after chronic ethanol treatment in the spinal cord.     

THE DISTRIBUTION OF GLYCINE, GABA, GLUTAMATE AND ASPARTATE IN RABBIT SPINAL CORD, CEREBELLUM AND HIPPOCAMPUS

The distribution of glycine, GABA, glutamate and aspartate was measured among about 60 subdivisions of rabbit spinal cord, and among the discrete layers of cerebellum, hippocampus and area dentata. A more detailed mapping for GABA was made within the tip of the dorsal horn of the spinal cord. Spinal ventral horn and dorsal root ganglion cell bodies were analyzed for the amino acids and for total lipid. The distribution of lipid and lipid-free dry weight per unit volume was also determined in spinal cord. Calculated on the basis of tissue water, glycine in the cord is highest in lateral and ventral white matter immediately adjacent to the ventral grey. The distribution of GABA is almost the inverse of that of glycine with highest level in the tip of dorsal horn. It is most highly concentrated in the central 75% of Rexed layers III and IV. Aspartate in the tip of ventral horn is 4-fold higher than in the tip of the dorsal horn and 3 times the average concentration in brain. Glutamate was much more evenly distributed and is relatively low in concentration with slightly higher levels in dorsal than in ventral grey matter. Large cell bodies in both ventral horn and dorsal root ganglion contained high levels of glycine. As reported by others, GABA was found to be high in cerebellar grey layers, area dentata, and regio inferior of hippocampus. Glycine was moderately high in cerebellar layers but moderate to low in hippocampus and area dentata.     

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.     

Characterization of antisera to glutamate and aspartate

Antisera were raised in rabbits against glutamate (Glu) and aspartate (Asp) conjugated to the invertebrate carrier protein hemocyanin (HC) with glutaraldehyde (GA). The antisera were characterized by testing their immunocytochemical staining properties on sections cut at the level of the ventral cochlear nucleus (VCN) from fixed brains of normal rats after absorption with conjugates of compounds structurally similar and biologically relevant to Glu and Asp. Optimal staining with Glu antiserum was obtained at a dilution of 1:10,000 and was completely blocked by 303 micrograms/ml of the Glu-HC conjugate. No crossreactivity with any of 11 compounds tested was observed. Optimal staining with the Asp antiserum was obtained at 1:8000 dilution and was completely blocked by 225 micrograms/ml of the Asp-HC conjugate. Of 10 compounds tested for crossreactivity, only L-asparagine demonstrated a measurable (about 10%) crossreactivity with the Asp antiserum. The specificity of the two antisera was also tested by immunoblot analysis against 11 compounds conjugated to HC with GA. Listed in order of staining intensity, from greatest to least, conjugates that reacted with the Glu antiserum were Glu greater than Gly-Glu greater than Asp-Glu = Asp greater than N-carbamyl (NC)-Glu greater than Asn = Gln = GABA. Conjugates that reacted with the Asp antiserum, in order of decreasing staining intensity, were Asp greater than Glu-Asp = Asn greater than Gly-Asp greater than Glu. No other compounds tested for crossreactivity reacted with the two antisera in the immunoblot analysis. Glu-like immunoreactivity in rat dorsal root ganglia and somatosensory cortex, and the comparative distribution of Glu- and Asp-like immunoreactivities in the latter tissue, are presented as examples of staining patterns obtained with the two antisera.     

Effects of GABA and Glycine on Postsynaptic Potentials of Motoneurons of the Frog <Emphasis Type="Italic">Rana ridibunda</Emphasis>

On a preparation of isolated spinal cord of the frog Rana ridibunda, using intracellular recording from lumbar motoneurons, there were compared effects of GABA and Gly on membrane potentials, membrane resistance, and EPSP evoked by activation of dorsal root fibers or of brainstem reticular formation. All parameters were compared in the same cell. At the same concentration (10 mM), Gly evoked membrane depolarization by 20–50% greater than GABA. Response of application of a mixture of GABA and Gly was by 20% lower than the arithmetic sum of responses to the GABA application and the Gly application. The late components and the semiwidth both of complex and of simpler DR and RF EPSP decreased significantly (to 95%) on the background of application of GABA and Gly. The late components of the both EPSP were inhibited stronger by GABA than by Gly. The early mono- and disynaptic EPSP components were inhibited to the essentially lesser degree than the late components. Gly always inhibited the early DR EPSP more markedly than GABA did. In the greater part of motoneurons the early RF EPSP were stronger inhibited by Gly, in their smaller part, by GABA. In many motoneurons the early components did not decrease at all. The motoneuron membrane resistance decreased under effect of GABA and Gly to the approximately equal extent (by 10–30%). Not in all neurons there was revealed the correspondence between a decrease of the membrane resistance (R_M) and a decrease of the early EPSP components. Based on the obtained data, it is suggested that the inhibitory influences in frogs is mediated by both Gly- and GABA-receptors. On the membrane of motoneuron the inhibition is mediated to the relatively greater degree by Gly-receptors, whereas on the membrane of interneurons, by GABA-receptors. During inhibition of DR EPSP the predominance of Gly-receptors is observed in the greater number of motoneurons than during inhibition of RF EPSP. Between individual motoneurons there are significant quantitative differences of all parameters.     

Distribution of neuropeptide Y in the spinal cords of cat, dog, rat, man and pig

Regional distribution of neuropeptide Y (NPY) in spinal cord, dorsal root ganglia (DRG) and peripheral nerves was quantitated in rat, cat, dog, pig, and man. Spinal cords were harvested post mortem and dissected into regions or individual segments. A further dissection into dorsal and ventral horns was carried out, and DRG were harvested in all species except rat. Tissues were extracted into boiling 0.1 M HCl, and NPY was measured by radioimmunoassay using a specific antibody and I125-labeled NPY. Highest concentrations of NPY were consistently found in the dorsal horn of the lumbo-sacral cord (200-800 ng/g). DRG concentrations, in contrast, were routinely low or undetectable. Sciatic nerve concentrations in rat and pig were considerable. High performance liquid chromatography (HPLC) confirmed that the NPY immunoreactivity measured in dorsal horns of each species coeluted with authentic NPY (1-36) as a single peak.     

Identification and Distribution of Neuroleptic Binding Sites in the Rat Spinal Cord

Identification of neuroleptic receptor sites in the rat spinal cord could be achieved by the binding of [3H]haloperidol to membranes taken from the different horns. The use of pooled frozen microdiscs punched from these different spinal cord areas allowed the detection of saturable stereospecific binding, as defined in the presence of (+)- and (-)-butaclamol. Comparison of the binding constants with those obtained in the corpus striatum resulted in similar dissociation constants and Hill's slopes. Maximal binding capacity was quite different, being the greatest in the whole striatum (157 +/- 8 fmol/mg protein) followed by the dorsal horn (56 +/- 3 fmol/mg protein) and the lateral (34 +/- 5 fmol/mg protein) and ventral ones (31 +/- 2 fmol/mg protein). The displacement of the labelled ligand by different dopaminergic and nondopaminergic drugs at various concentrations gave similar results in the whole striatum and the spinal cord, giving further support for the existence of a dopaminergic innervation of the spinal cord and showing that dopaminergic receptor sites are distributed through the different spinal horns, with a maximal density in the dorsal horn--as for dopamine levels. No detectable stereospecific binding could be obtained from the surrounding spinal white matter, even at high tissue concentrations. Owing to poor sensitivity of the binding technique, no stereospecific neuroleptic binding could be demonstrated in the whole spinal cord, even at very high tissue concentration, whereas it could be detected in spinal cord tissue sampled from restricted areas of dense dopaminergic innervation.     

Regional Distribution of Phospholipids and Polyphosphatidyl Inositides in the Rabbit's Spinal Cord

The plasticity of the membrane phospholipids in general and stimulated phosphoinositides turnover in particular are the subjects in a variety of neural paradigms studying the molecular mechanisms of neuronal changes under normal and pathological conditions. The regional modifiability of phospholipids (SM, PC, PS, PI, PA + DG, PE), polyphosphatidylinositides (PI, PIP, PIP₂) and diacylglycerol-dependent incorporation of CDP-choline into phosphatidylcholine in the gray matter, white matter, dorsal horns, intermediate zone and ventral horns of the rabbit's spinal cord was studied. We have found 1. a significant increase in the concentration of SM, PC, PS, DG + PA and PE in the white matter in comparison to the gray one, 2. the highest concentration of the outer membrane leaflet-bound phospholipids in the dorsal horns and the inner membrane phospholipids in the intermediate zone in comparison to the gray matter, 3. a substantial amount of labeled polyphosphatidylinositides (poly-PI_s) in the spinal cord white matter with descending order PIP > PI > PIP₂, 4. similar incorporation of myo-2-[³H]inositol into all poly-PI_s in ventral horns and intermediate zone, but a different, lower incorporation into PI and PIP and higher into PIP₂ in the dorsal horns, 5. higher diacylglycerol-dependent incorporation of CDP-choline into PC in the regionally undivided gray matter than in the white matter taken as a whole, 6. the high proportion of diacylglycerol-dependent incorporation of CDP-choline into PC in both the ventral and dorsal horns, whereas that in the intermediate zone remained low.     

Arylamidase activity in the rabbit spinal cord after ligation of the abdominal aorta

Effect of ischaemia, induced by abdominal aorta occlusion, and subsequent survival on the activity of arylamidases was studied in the lumbar and cervical spinal cord of the rabbit. No effect of 40 min ischaemia on the activity of arylamidases was found either in homogenates or in subcellular fractions of the spinal cord. In the lumbar spinal cord a moderate decrease in arylamidase activity was observed after 1 day of survival and a marked decrease was found after 4 days. The decrease were localized in the microsomal and, particularly, in the cytosole fraction. No changes were found in the cervical spinal cord at the corresponding intervals.     

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。