Effect Of L-glutamic Acid Research Articles

Effect of L-glutamic acid as hydrogen generation inhibitor on aluminum waste

Aluminum on reaction with water generates hydrogen, aluminum waste (AW) under moist condition causes hydrogen blast. To inhibit the evolution of hydrogen during the reaction of aluminum with water, environmentally friendly L-glutamic acid (GA)was utilized. The results of hydrogen generation experiment show that 0.3 g GA with 0.5 g AW and 0.5 g sodium borohydride (NH) has the ability to suppress the hydrogen generation reaction. The XRD, FTIR and SEM analysis indicate the presence of protective covering film of GA is formed on the surface of AW, blocking the reaction to occur between aluminum with water. This study addresses the lack of research on inhibitors for hydrogen fire blasts when removing wet aluminum dust.

Investigation of Foliar L-Glutamic Application on the Resistance to the Capacity of the SC2121 Tomato Variety (Solanum lycopersicum L.) to Long-Term Salinity Stress

Within the scope of this study, the effects of L-Glutamic acid (L-GLU: 250 mg L-1, 500 mg L-1) treatments on morphological and biochemical characteristics of SC2121 tomato variety under salt stress (50 mM, 100 mM, 200 mM NaCl) were compared. The morphological results obtained from leaves and fruits were found to peak at 500GLU, 50NaCl-500GLU, 250GLU, and 200NaCl-500GLU, whereas their lowest values were achieved with doses of 200NaCl, 200NaCl-250GLU, 100NaCl, and 100NaCl-500GLU Among the bioactive molecules, amino acid, and proline amounts increased in all the treatments, whereas total protein increased in 500GLU and 50NaCl- 250GLU, 50NaCl-500GLU. CAT activity increased in doses of 500GLU and 50 NaCl-250GLU, 50NaCl-500GLU, whereas POD and SOD activity decreased in high NaCl and 200NaCl+ 250GLU, 200NaCl-500GLU. Treatments caused an increase in MDA concentration, while NaCl (50-100 mM), GLU, and 100 NaCl-500GLU reduced the H2O2 concentration. In conclusion, 500GLU, 50NaCl-500GLU, 50NaCl-250GLU, 250GLU, and 200NaCl+500GLU stimulated the growth and development in the SC2121 tomato variety, as well as the leaf bioactive chemicals. However, 200NaCl-250GLU, 200NaCl, and 200NaCl-250GLU reduced the growth and development of the tomato and decreased the chemicals in the leaves. Given the results, it can be stated that yield and quality could be increased by making use of GLU treatments in tomato varieties under salt stress.

Effects of glutamic acid applications on the yield and growth parameters in garlic (Allium sativum L.) cultivation

Since exogenous amino acid applications to agricultural plants provide ready mineral nutrition for plants, they are widely used to enhance the yield and quality of crops as well as to strengthen resistance to environmental impacts. In the present study, the effects of L-Glutamic acid (GLU) (100, 200, 400, 800, and 1000 mg L-1) treatments on the growth parameters, bulb yield, chemical contents, and weight loss of Taşköprü garlic were analyzed. Given the findings, 800 GLU dose was found to have the highest values in shoot length and width, fresh weight, width, and length of the bulb, length and of large and small cloves, and yield per plot. On the other hand, the lowest results in total free amino acid, nitrate, polyphenol, ascorbic acid, and % ash amounts were obtained with 400 GLU, while the maximum leaf length and width was obtained with 1000 GLU dose. The first and third weight losses were obtained in 100 GLU and control groups and the second weight loss value obtained in all groups were higher than in the control. Considering all the data, the doses of 800 GLU and 400 GLU yielded the most positive effect on growth parameters, bulb yield, and weight loss measurements in garlic, whereas the lowest level of effect was observed in the control and 100 GLU groups. In conclusion, it can be stated that the foliar application of L-Glutamic acid in garlic cultivation might increase the yield and quality.

Effect of L-Glutamic Acid on the Composition and Morphology of Nanostructured Calcium Phosphate as Biomaterial.

Calcium phosphate (CaP) with several chemical compositions and morphologies was prepared by precipitation using aqueous solutions of L-Glutamic acid (H2G) and calcium hydroxide, both mixed together with an aqueous solution (0.15 M) of phosphoric acid. Plate-shaped dicalcium phosphate dihydrate (brushite) particles were obtained and identified at a lower concentration of the solution of the reactants. The Ca/P ratio deduced by EDS was ~1, as expected. The nanoscale dimension of carbonate apatite and amorphous calcium phosphate, with variable Ca/P ratios, were revealed by X-ray diffraction (XRD) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). They were characterized in medium and high concentrations of calcium hydroxide (0.15 M and 0.20 M). The equilibria involved in all the reactions in aqueous solution were determined. The thermodynamic calculations showed a decrease in the amount of chelate complexes with an increase in pH, being the opposite of [CaPO4-] and [CaHG+]. This fluctuation showed an evident influence on the morphology and polymorphism of CaP particles obtained under the present experimental conditions, with potential use as a biomaterial.

Дія L-глутамінової кислоти на зміни біохімічних показників щурів, інтоксикованих тетрахлорметаном

This study aims to explore the ameliorative effects of L-glutamic acid (L-Glu) against carbon tetrachloride (CCl4) toxicity in male rats. Changes in the activities of alanine and aspartate aminotransferases (ALAT, ASAT) were studied in the tissues and blood of rats. Concentrations of creatinine, triacylglycerol and cholesterol were also determined in the blood of experimental animals. Intraperitoneal administration of CCl4 to rats led to changes in the blood of animals of the studied parameters — an increase of the activities of aminotransferases, triacylglycerol and cholesterol levels. At the same time, a decrease of ALAT activity was observed in the tissues of the myocardium and spleen of intoxicated animals, ASAT in their brain, and in the tissues of the lungs there was an increase in the activity of ALAT and the growth of ASAT in the tissues of the spleen In turn, with additional administration to animals intoxicated with tetrachloromethane L-Glu mitigation or no change in most of the studied indicators was observed, namely, in the blood the activity of ASAT fluctuated within the control values, and the concentrations of triacylglycerol and cholesterol did not change compared to the control. Also under the action of the studied aminoacid, no changes were detected in the activities of ALAT in lung tissue and ASAT in spleen tissue. The obtained results indicate a corrective effect of L-Glu on the physiological and biochemical parameters of rats in their intoxication with carbon tetrachloride.

Effect of L-glutamic acid N,N-diacetic acid on the availability of dietary zinc in broiler chickens

Chelating agents can be used to improve the nutritional availability of trace minerals within the gastrointestinal tract. This study was conducted to determine the effect of a novel chelating agents, L-glutamic acid N,N-diacetic acid (GLDA), a biodegradable alternative to ethylenediaminetetraacetic acid on the nutritional bioavailability of zinc in broilers. Twelve dietary treatments were allocated to 96 pens in a randomized block design. Pens contained 10 Ross 308 male broilers in a factorial design with 6 incremental zinc levels (40, 45, 50, 60, 80, and 120 ppm of total Zn), with and without inclusion of GLDA (0 and 100 ppm) as respective factors. Experimental diets were supplied from day 7 to 21/22 and serum, liver and tibia Zn content were determined in 3 birds per pen. Growth performance and liver characteristics were not affected by dietary treatments, but both supplemental Zn and GLDA enhanced tibia and serum zinc concentration. The positive effect of GLDA was observed at all levels of the dietary Zn addition. The amount of zinc needed to reach 95% of the asymptotic Zn response was determined using nonlinear regression. When GLDA was included in the diet, based on tibia Zn, the same Zn status was achieved with a 19 ppm smaller Zn dose while based on serum Zn this was 27 ppm less Zn. Dietary GLDA reduces supplemental Zn needs to fulfill nutritional demands as defined by tibia Zn and serum Zn response. Considering the positive effect on the nutritional availability of Zn in broilers, GLDA presents an opportunity as biodegradable additive, to reduce Zn supplementation to livestock and thereby reducing Zn excretion into the environment, while fulfilling the nutrition Zn needs of farmed animals.

Effects of L-glutamic acid, N, N-diacetic acid as chelating agent on acidification of carbonate reservoirs in acidic environments

For matrix acidification in carbonate reservoirs, the use of chelating agents can avoid the problems associated with conventional acids, such as excessive acid-rock reaction and extreme corrosion on a well tubular. L-glutamic acid, N, N-diacetic acid (GLDA) has been used as a chelating agent for carbonate reservoir stimulation owing to its high water solubility, effective dissolution effect on carbonate, lower corrosion to metals than conventional acid, and high biodegradability. In this study, the dissolution and acidification effect of GLDA on Baota limestone, as well as its corrosion effect on a well tubular and iron control capabilities, were evaluated. Meanwhile, the mechanism of GLDA on Baota limestone was studied by inductively coupled plasma optical emission spectrometer (ICP-OES), zeta potential, and core flooding experiments at low pH, which was adjusted using a conventional acid. The results indicated that 5% GLDA with the pH adjusted by acetic acid (pH = 4, HAC) exhibited the most significant acidification effect on the Baota limestone. Its dissolution rates were 75.2 and 94.4% at 25 and 80 °C, respectively, after 16 h. The surface of the Baota limestone was mainly positively charged in the aqueous solution; thus, the negatively charged GLDA was easily absorbed and chelated. In terms of iron control and corrosion inhibition, 5% GLDA (pH = 4, HAC) performed better than 5% GLDA, 5% HAC, and 5% HCl. The corrosion rate of 5% GLDA (pH = 4, HAC) on P110 metal test pieces were only 0.74 and 14.43 g/(m2·h) at 25 and 80 °C, respectively, for 24 h, which showed more noticeable corrosion inhibition effects than 5% HCl (2.08 and 56.10 g/(m2·h) at 25 and 80 °C, respectively). Based on the core flooding experiment and computed tomography (CT) scanning, it was determined that 3% GLDA (pH = 4, HAC) had the most significant acidification effect on the Baota limestone at an injection rate of 1 mL/min. The permeability and porosity of the Baota limestone increased from 0.12 to 5.8 mD (approximately 48x) and from 0.44 to 2.22%, respectively. The findings of this study may provide an effective reference guide for matrix acidification design of carbonate reservoirs.

Дія L-глутамінової кислоти та N-ацетилцистеїну на імунологічні та гематологічні показники за дії CCL4-індукованого стресу у щурів

Дія L-глутамінової кислоти та N-ацетилцистеїну на імунологічні та гематологічні показники за дії CCL4-індукованого стресу у щурів

Effects of L-glutamic acid and pyridoxine on glutathione depletion and lipid peroxidation generated by epinephrine-induced stress in rats

Effects of L-glutamic acid and pyridoxine on glutathione depletion and lipid peroxidation generated by epinephrine-induced stress in rats

Comparison of Neurotropic Effects of L-Glutamic Acid and Its New Derivative β-Phenylglutamic Acid Hydrochloride (RGPU-135, Glutarone)

In contrast to L-glutamic acid (200 mg/kg), β-phenylglutamic acid hydrochloride (26 mg/kg) produces no anticonvulsant effects during generalized convulsions induced by "maximum electric shock". However, β-phenylglutamic acid hydrochloride was more potent than L-glutamic acid in increasing survival rate, promoting recovery of spontaneous motor activity, and maintainance locomotor and exploratory activity in the open field test and cognitive functions in conditioned passive avoidance test, i.e. exhibited neuroprotective activity. This substance did not change the threshold of pain induced by electric stimulation of paws (up to vocalization) and thermal tail stimulation (tail-flick), whereas L-glutamic acid decreased this parameter. β-Phenylglutamic acid suppressed aggression in the test for provoked unmotivated aggression, while L-glutamic acid enhanced it. Due to these neurotropic effects, β-phenylglutamic acid hydrochloride can be used as the basis for the development of drugs with antidepressant, anxiolytic, and neuroprotective actions.

Effect of l-glutamic acid on the positive electrolyte for all-vanadium redox flow battery

l-Glutamic acid is used as an additive for the positive electrolyte of all-vanadium redox flow battery (VRFB), and its effect on the thermal stability and electrochemical activity is investigated. It is found that the addition of l-glutamic can significantly alleviate the precipitation of V2O5 from positive electrolyte. The conservation rate of V(V) ion can be as high as 58% after 2M V(V) solution being kept in 40°C for 89h. Besides, l-glutamic can also improve the mass transport and electrochemical performance of anolyte. A high coulombic efficiency of over 95% and energy efficiency of 74% are obtained. XPS spectra illustrate that l-glutamic can react with the surface of carbon felt electrode and introduce more oxygen-containing and nitrogen-containing groups, which should be responsible for the improvement of electrochemical performance.

Glutamine and glutamic acid enhance thyroid-stimulating hormone β subunit mRNA expression in the rat pars tuberalis

Thyroid-stimulating hormone (TSH)-producing cells of the pars tuberalis (PT) display distinct characteristics that differ from those of the pars distalis (PD). The mRNA expression of TSHβ and αGSU in PT has a circadian rhythm and is inhibited by melatonin via melatonin receptor type 1; however, the detailed regulatory mechanism for TSHβ expression in the PT remains unclear. To identify the factors that affect PT, a microarray analysis was performed on laser-captured PT tissue to screen for genes coding for receptors that are abundantly expressed in the PT. In the PT, we found high expression of the KA2, which is an ionotropic glutamic acid receptor (iGluR). In addition, the amino acid transporter A2 (ATA2), also known as the glutamine transporter, and glutaminase (GLS), as well as GLS2, were highly expressed in the PT compared to the PD. We examined the effects of glutamine and glutamic acid on TSHβ expression and αGSU expression in PT slice cultures. l-Glutamine and l-glutamic acid significantly stimulated TSHβ expression in PT slices after 2- and 4-h treatments, and the effect of l-glutamic acid was stronger than that of l-glutamine. In contrast, treatment with glutamine and glutamic acid did not affect αGSU expression in the PT or the expression of TSHβ or αGSU in the PD. These results strongly suggest that glutamine is taken up by PT cells through ATA2 and that glutamic acid locally converted from glutamine by Gls induces TSHβ expression via the KA2 in an autocrine and/or paracrine manner in the PT.

Characterization of crystallisation processes with electrical impedance spectroscopy

The surfaces of crystalline particles are often charged and therefore crystals have an electrical double layer associated with their surfaces when, for example, suspended in an aqueous medium. Under the influence of an external electric field, an electrical dipole moment can be induced due to polarization of the electrical double layer. The complex impedance, conductivity, relaxation time and phase shift caused by the polarization are all related to particle characteristics, e.g. the size, polymorph and concentration. The method of electrical impedance spectroscopy (EIS) provides, potentially, a capability for characterizing the particles in colloidal suspensions. Here some preliminary observations of physical-chemistry fundamentals relating to the use of electrical impedance spectroscopy, potentially, for particle sizing in crystallisation processes are reported. Firstly, the effects of l-glutamic acid (LGA) solids concentration, solute concentration and temperature on the measured EIS spectra were studied. The results show that the effects of solid LGA concentration and solute concentration on the relaxation frequency and phase angle are very small. Secondly, the temperature effect was analysed. By deducting the contribution due to the changes in concentration and temperature from the total change in relaxation frequency, the experimental observations, although preliminary in nature, suggest that the crystal size can be related directly to relaxation frequency (in this study, the shape of LGA crystals is assumed to be spherical so the crystal size means the diameter of the sphere). The experimental observations can be explained with either static polarization models or particle vibration models. On-line measurement of electrical impedance spectra associated with LGA nucleation–growth processes are presented. The information content of the complex electrical impedance, phase angle shift and relaxation times of the crystal suspensions during a crystallisation process is assessed. The results show that during nucleation the imaginary part of the electrical-impedance response changes significantly and the relaxation frequency decreases during the growth of crystals. The longer-term objective is to develop a new spectroscopic measurement method and further, a spectroscopic tomography technique for on-line measurement of the spatial distribution of particle size in particle suspensions in liquid media.

Electrochemical characterization of copper chemical mechanical polishing in l-glutamic acid–hydrogen peroxide-based slurries

The effect of l-glutamic acid as complexing agent in the presence of hydrogen peroxide as oxidizer in copper chemical mechanical polishing (CMP) slurry is investigated. In the CMP process, the work surface is moved against a pad, with slurry flowing between the surface and the pad. The polish rate was found to be stable over a wide range of hydrogen peroxide concentration. High concentration of either l-glutamic acid or hydrogen peroxide leads to a reduction in polish rate, but a high concentration of both chemicals does not reduce the polish rate. In the absence of hydrogen peroxide, the Cu polish rate was 0 for all the l-glutamic acid concentrations investigated. However, potentiodynamic polarization curves do not show any sign of passivation when l-glutamic acid was present in the solution. In situ open circuit potential measurements show that copper redox reactions as well as hydrogen peroxide redox reactions contribute in determining the electrochemical behavior. We propose that l-glutamic acid inhibits the copper dissolution by adsorption onto the metallic copper, but enhances copper dissolution by complexing copper ions. The results show that it is possible to conduct controllable copper CMP in mildly acidic slurries with hydrogen peroxide as oxidizer and l-glutamic acid as complexing agent.

Efeitos do ácido L-glutâmico e da vitamina K na composição bioquímica parcial de fêmures de frangos de corte

Objetivou-se estudar os efeitos da combinação de ácido L-glutâmico (L-Glu) e vitamina K na composição bioquímica de fêmures (proteínas colagenosas; não-colagenosas e totais) de frangos de corte. O experimento, que teve 14 dias de duração, foi conduzido em delineamento inteiramente casualizado, em fatorial 2 × 4, com dois níveis de ácido L-glutâmico (6,25 e 12,5%) combinados com quatro níveis de vitamina K (0,02; 0,2; 2,0 e 20,0 mg/kg de ração), cada combinação com quatro repetições de dez animais. Foram utilizados pintos machos, Avian Farm, de 1 dia, criados em baterias aquecidas e alimentados à vontade com dieta básica contendo L-aminoácidos essenciais, minerais e vitaminas (exceto vitamina K) suplementada com ácido L-glutâmico e vitamina K. Ao término do experimento, os animais foram sacrificados por deslocamento cervical e seus fêmures removidos, medidos, desengordurados e pesados. Não foi observada interação significativa entre ácido L-glutâmico e vitamina K para os parâmetros estudados. Os teores de proteínas não-colagenosas foram maiores e o de proteínas colagenosas, menores nos fêmures dos pintos alimentados com a ração com 6,25% de ácido L-glutâmico. Os teores de proteínas totais, no entanto, não foram afetados pelos níveis de ácido L-glutâmico e de vitamina K. Os níveis de vitamina K tiveram efeito quadrático decrescente nos teores de proteínas não-colagenosas e efeito crescente na composição de proteínas colagenosas dos fêmures. A composição em proteínas colagenosas e não-colagenosas pode ser utilizada como indicador bioquímico de anormalidades de pernas causadas por baixo nível de nitrogênio não-específico.

0699 The effect of L-glutamic acid and Norharman on brotizolam induced anterograde and retrograde amnesia in mice using Morris water maze task

0699 The effect of L-glutamic acid and Norharman on brotizolam induced anterograde and retrograde amnesia in mice using Morris water maze task

Glutamate regulation of dopamine release in guinea pig striatal slices

The effect of l-glutamic acid ( l-Glu) on basal and electrically evoked [ 3H]-dopamine efflux in guinea pig striatal slices was studied. In the presence of magnesium, l-Glu significantly increased spontaneous [ 3H]-dopamine efflux. This response was unaffected by the non-NMDA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the non-competitive NMDA receptor antagonist, d-5-methyl-10,11,dihydro-5-H-dibenzo-[ a,d]-cyclohepten-5,10-imine maleate (MK-801), the glycine antagonist 7-chlorokynurenic acid (7-CL-KYN) and by the metabotropic receptor antagonist (+)-α-methyl-4-carboxyphenyl-glycine (α-M4CPG) and l-2-amino-3-phosphonopropionic acid ( l-AP3). However, the metabotropic glutamate receptor agonist, trans-1-aminocyclopentane-1,3-dicarboxylic acid ( t-ACPD), increased spontaneous [ 3H]-dopamine efflux, as did l-Glu, and this response was completely counteracted by α-M4CPG. In the absence of magnesium, l-Glu induced a concentration-dependent increase in basal [ 3H]-dopamine efflux, which was prevented by MK-801. In electrically stimulated striatal slices l-Glu, applied 25 min before the stimulation, concentration-dependently increased the [ 3H]-dopamine efflux both in the presence and in the absence of magnesium. This effect was completely prevented by CNQX, but not by MK-801 or dl-2-amino-5-phosphono-pentanoic acid (AP5). On the contrary, l-Glu, applied during electrical stimulation (2 min) in the absence of Mg 2+, increased the [ 3H]-dopamine efflux to 200%, and this effect was partly counteracted by MK-801. These results provide evidence that different subtypes of excitatory amino acid receptors modulate [ 3H]-dopamine efflux depending on the functional state (rest or activity) of the nerve endings. The spontaneous [ 3H]-dopamine efflux appears to be controlled by metabotropic receptors in the presence of Mg 2+ and by NMDA receptors in its absence. Conversely, the AMPA/kainate receptors facilitate the electrically evoked [ 3H]-dopamine efflux in the presence of Mg 2+, whereas the NMDA receptors appeared to be operative, in the absence of Mg 2+, as long as l-Glu was applied simultaneously with the electrical stimulation.

Effects of l-glutamic acid and its agonists on snail neurones

The sensitivities of 22 giant neurone types of an African giant snail ( Achatina fulica Férussac) to threo-β-hydroxy- l-glutamic acid (threo- l-BHGA), a derivative of l-glutamic acid ( l-Glu), applied by brief pneumatic pressure ejection, were examined under current clamp. The 5 neurone types were depolarized by this compound, whereas 2 were hyperpolarized. The 4 neurone types, PON (periodically oscillating neurone), RAPN (right anterior pallial nerve neurone), d-RPLN (dorsal-right parietal large neurone) and RPeNLN (right pedal nerve large neurone) that are excited by threo- l-BHGA and one type, v-LCDN (ventral-left cerebral distinct neurone), inhibited by this compound, were selected to study their pharmacological features in detail. Effects of the stereoisomers of l-Glu and threo- l-BHGA, and mammalian l-Glu receptor agonists, ejected by brief pressure, on the 5 Achatina neurone types were examined under voltage clamp. d-RPLN produced an inward current (I in) by l-Glu and threo- l-BHGA, whereas this neurone type was insensitive to D-Glu and erythro-L-, threo-D- and erythro-D-BHGA. This was also excited by AMPA, indicating that the pharmacological features of the l-Glu receptors in this neurone type were similar to those of the mammalian ionotropic AMPA type L-Glu receptors. RAPN produced I in by l-Glu and threo- l-BHGA. This neurone type was also excited by quisqualic acid and ibotenic acid, indicating that the features of the l-Glu receptors were similar to those of the mammalian metabotropic l-Glu receptors. PON and RPeNLN produced I in, by l-Glu and threo- l-BHGA. These neurone types were also excited by quisqualic acid, AMPA and ibotenic acid, indicating that their l-Glu receptors seemed to be in the mixed type, of the two types mentioned. On the other hand, v-LCDN produced an outward current (I out) by threo- l- and erythro- l-BHGA, but was insensitive to L-Glu, indicating that the receptors activated by l-BHGA were not l-Glu receptors. This neurone type was also inhibited by quisqualic acid.

Novel heteroaryl-spaced APV and APH analogs as ligands for the NMDA receptor : S.J. Hays, C.F. Bigge, J.T. Drummond, G. Johnson, L.J. Brahce, L.L. Coughenour, L.J. Robichaud, A.W. Probert and P.A. Boxer. Parke-Davis Pharmaceutical Research Division, Warner Lambert Company, Ann Arbor, MI. USA

The effect of l-glutamic acid (l-Glu) on basal and electrically evoked [3H]-dopamine efflux in guinea pig striatal slices was studied. In the presence of magnesium, l-Glu significantly increased spontaneous [3H]-dopamine efflux. This response was unaffected by the non-NMDA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the non-competitive NMDA receptor antagonist, d-5-methyl-10,11,dihydro-5-H-dibenzo-[a,d]-cyclohepten-5,10-imine maleate (MK-801), the glycine antagonist 7-chlorokynurenic acid (7-CL-KYN) and by the metabotropic receptor antagonist (+)-α-methyl-4-carboxyphenyl-glycine (α-M4CPG) and l-2-amino-3-phosphonopropionic acid (l-AP3). However, the metabotropic glutamate receptor agonist, trans-1-aminocyclopentane-1,3-dicarboxylic acid (t-ACPD), increased spontaneous [3H]-dopamine efflux, as did l-Glu, and this response was completely counteracted by α-M4CPG.In the absence of magnesium, l-Glu induced a concentration-dependent increase in basal [3H]-dopamine efflux, which was prevented by MK-801.In electrically stimulated striatal slices l-Glu, applied 25 min before the stimulation, concentration-dependently increased the [3H]-dopamine efflux both in the presence and in the absence of magnesium. This effect was completely prevented by CNQX, but not by MK-801 or dl-2-amino-5-phosphono-pentanoic acid (AP5). On the contrary, l-Glu, applied during electrical stimulation (2 min) in the absence of Mg2+, increased the [3H]-dopamine efflux to 200%, and this effect was partly counteracted by MK-801.These results provide evidence that different subtypes of excitatory amino acid receptors modulate [3H]-dopamine efflux depending on the functional state (rest or activity) of the nerve endings. The spontaneous [3H]-dopamine efflux appears to be controlled by metabotropic receptors in the presence of Mg2+ and by NMDA receptors in its absence. Conversely, the AMPA/kainate receptors facilitate the electrically evoked [3H]-dopamine efflux in the presence of Mg2+, whereas the NMDA receptors appeared to be operative, in the absence of Mg2+, as long as l-Glu was applied simultaneously with the electrical stimulation.

Effects of intrahypothalamic injections of GABA, muscimol, pentobarbital, and L-glutamic acid on feed intake of satiated sheep

Five wethers were surgically prepared with cranial implants to study the role of gabaminergic neural pathways on the hypothalamic control of feeding behaviour in ruminants. In the first experiment, the animals were injected (1 microL) with a physiological Tyrode (0.95%) solution, muscimol (0.5 and 1.0 nmol), GABA (0.5 and 1.0 nmol), and L-glutamic acid (0.5 and 1.0 nmol). Feed intake following injections of muscimol (1.0 nmol) and L-glutamic acid (0.5 and 1.0 nmol) was twice as large as that following the Tyrode solution, at 60-min postinjections. These results, however, were not statistically significant (p = 0.12-0.15). In the second experiment, the animals were injected (1 microL) with saline, muscimol (0.8 nmol), L-glutamic acid (0.8 nmol), and pentobarbital (0.26 mumol). Fifteen minutes after the injections, pentobarbital had induced a significant feeding response when compared with control values (p less than 0.01), whereas the effect of L-glutamic acid was not significant. However, 30 min after the injections, feed intake of sheep having received L-glutamic acid was higher than that obtained with the control injections (p less than 0.01). The response to pentobarbital was stronger than that to either muscimol or L-glutamic acid. Histological analyses of brain tissue indicated that injections were performed in the ventromedial hypothalamus of four sheep and in the dorsomedial hypothalamus of the other. The data indicate that L-glutamic acid stimulates feed intake by acting either as a precursor of GABA or by a direct stimulation of glutaminergic neural pathways involved in the control of feed intake.