Uptake In Slices Research Articles

Piperazic acid and related compounds as inhibitors of GABA uptake in rat brain slices.

Journal Article Piperazic acid and related compounds as inhibitors of GABA uptake in rat brain slices Get access G A R Johnston, G A R Johnston Department of Pharmacology, Australian National University, Canberra, Australia Correspondence: Department of Pharmacology, Australian National University, Canberra, Australia Search for other works by this author on: Oxford Academic Google Scholar A L Stephanson, A L Stephanson Department of Pharmacology, Australian National University, Canberra, Australia Search for other works by this author on: Oxford Academic Google Scholar B Twitchin B Twitchin Department of Pharmacology, Australian National University, Canberra, Australia Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 29, Issue 1, September 1977, Pages 240–241, https://doi.org/10.1111/j.2042-7158.1977.tb11297.x Published: 12 April 2011 Article history Received: 29 October 1976 Published: 12 April 2011

Chronic Stress and Lithium Treatments Alter Hippocampal Glutamate Uptake and Release in the Rat and Potentiate Necrotic Cellular Death After Oxygen and Glucose Deprivation

This study was undertaken to evaluate the effects of chronic variate stress and lithium treatment on glutamatergic activity and neuronal vulnerability of rat hippocampus. Male Wistar rats were simultaneously treated with lithium and submitted to a chronic variate stress protocol during 40days, and afterwards the hippocampal glutamatergic uptake and release, measured in slices and synaptosomes, were evaluated. We observed an increased synaptosomal [(3)H]glutamate uptake and an increase in [(3)H]glutamate stimulated release in hippocampus of lithium-treated rats. Chronic stress increased basal [(3)H]glutamate release by synaptosomes, and decreased [(3)H]glutamate uptake in hippocampal slices. When evaluating cellular vulnerability, both stress and lithium increased cellular death after oxygen and glucose deprivation (OGD). We suggest that the manipulation of glutamatergic activity induced by stress may be in part responsible for the neuroendangerment observed after stress exposure, and that, in spite of the described neuroprotective effects of lithium, it increased the neuronal vulnerability after OGD.

Impaired dopamine release and uptake in R6/1 Huntington's disease model mice

Huntington's disease (HD) is a progressive, neurodegenerative movement disorder. Here, we used fast-scan cyclic voltammetry to measure dopamine release and uptake in striatal brain slices from R6/1 HD model mice. Peak dopamine release ([DA] max) was significantly diminished in R6/1 mice (52% of wild-type at 24 weeks of age). Similarly, dopamine released per locally applied electrical stimulus pulse ([DA] p), which is [DA] max corrected for uptake and electrode performance, was also diminished in R6/1 mice (43% of wild-type by 24 weeks of age). Moreover, V max, the maximum rate of dopamine uptake, obtained by modeling the stimulated release plots, was decreased at 16 and 24 weeks of age in R6/1 mice (51 and 48% of wild-type, respectively). Thus, impairments in both dopamine release and uptake appear to progress in an age-dependent manner in R6/1 mice.

Ascorbate uptake is decreased in the hippocampus of ageing rats

Ascorbate, an intracellular antioxidant, has been considered critical for neuronal protection against oxidant stress, which is supported especially by in vitro studies. Besides, it has been demonstrated an age-related decrease in brain ascorbate levels. The aims of the present study were to investigate ascorbate uptake in hippocampal slices from old Wistar rats, as well as its neuroprotective effects in in vitro and in vivo assays. Hippocampal slices from male Wistar rats aged 4, 11 and 24 months were incubated with radiolabeled ascorbate and incorporated radioactivity was measured. Hippocampal slices from rats were incubated with different concentrations of ascorbate and submitted to H 2O 2-induced injury, cellular damage and S100B protein levels were evaluated. The effect of chronic administration of ascorbate on cellular oxidative state and astrocyte biochemical parameters in the hippocampus from 18-months-old Wistar rats was also studied. The ascorbate uptake was decreased in hippocampal slices from old-aged rats, while supplementation with ascorbate (2 weeks) did not modify any tested oxidative status in the hippocampus and the incubation was unable to protect hippocampal slices submitted to oxidative damage (H 2O 2) from old rats. Our data suggest that the decline of ascorbate uptake might be involved in the brain greater susceptibility to oxidative damage with advancing age and both in vitro and vivo assays suggest that ascorbate supplementation did not protect hippocampal cells.

Differential transition metal uptake and fluorescent probe localization in hippocampal slices

Metals are taken up by the combined action of metal transporters and ion channels. In this communication we have measured the uptake of the biologically important transition metals Mn, Fe, Co, Ni, Cu, Zn and Cd by rat and mouse hippocampal slices using the fluorescent probes FluoZin-3 (FZ3) and Newport Green (NPG), introduced by acetoxymethyl ester (AM) loading. The combination of metals and probes is also used to attempt to localize cellular sites into which metals translocate. We show that FZ3 and NPG partition into different cellular compartments; FZ3 into neuropil, whereas NPG localizes in neuropil and compartments within the cell bodies of neurons. Ni, Zn and Cd pass across the plasma membrane and then accumulate in intracellular vesicles and within intracellular membranes of cell bodies. The latter accumulate Cd, while synaptic vesicles take up Co. The passage of Mn, Cu and Fe into cells can be detected but there is some uncertainty about their disposition within the cell. All of our experiments are consistent with metals accumulating in intracellular compartments rather than the cytoplasm. Whether and to what extent there are transient elevations of free zinc levels in the cytoplasm remains unclear.

Measurement of Unbound Drug Exposure in Brain: Modeling of pH Partitioning Explains Diverging Results between the Brain Slice and Brain Homogenate Methods

Currently used methodology for determining unbound drug exposure in brain combines measurement of the total drug concentration in the whole brain in vivo with estimation of brain tissue binding from one of two available in vitro methods: equilibrium dialysis of brain homogenate and the brain slice uptake method. This study of 56 compounds compares the fraction of unbound drug in brain (f(u,brain)), determined using the brain homogenate method, with the unbound volume of distribution in brain (V(u,brain)), determined using the brain slice method. Discrepancies were frequent and were primarily related to drug pH partitioning, attributable to the preservation of cellular structures in the slice that are absent in the homogenate. A mathematical model for pH partitioning into acidic intracellular compartments was derived to predict the slice V(u,brain) from measurements of f(u,brain) and drug pK(a). This model allowed prediction of V(u,brain) from f(u,brain) within a 2.2-fold error range for 95% of the drugs compared with a 4.5-fold error range using the brain homogenate f(u,brain) method alone. The greatest discrepancies between the methods occurred with compounds that are actively transported into brain cells, including gabapentin, metformin, and prototypic organic cation transporter substrates. It was concluded that intrabrain drug distribution is governed by several diverse mechanisms in addition to nonspecific binding and that the slice method is therefore more reliable than the homogenate method. As an alternative, predictions of V(u,brain) can be made from homogenate f(u,brain) using the pH partition model presented, although this model does not take into consideration possible active brain cell uptake.

Effects of Depressive-Like Behavior of Rats on Brain Glutamate Uptake

Learned helplessness paradigm is a widely accepted animal model of depressive-like behavior based on stress. Glutamatergic system is closely involved with the stress-neurotoxicity in the brain and recently it is pointed to have a relevant role in the pathophysiology of depression disorder. Glutamate uptake is the main mechanism to terminate the glutamatergic physiological activity and to neuroprotection against excitotoxicity. We investigated the profile of glutamate uptake in female rats submitted to the learned helplessness paradigm and to different classes of stress related to the paradigm, in slices of brain cortex, striatum and hippocampus. Glutamate uptake in slices of hippocampus differ between learned helplessness (LH) and non-learned helplessness (NLH) animals immediately persisting up to 21 days after the paradigm. In addition, there were a decrease of glutamate uptake in the three brain structures analyzed at 21 days after the paradigm for LH animals. These results may contribute to better understand the role of the glutamatergic system on the depressive-like behavior.

The effect of frying conditions on moisture loss and oil uptake in yam slices (Dioscorea alata)

The effect of frying conditions on immersion on moisture loss and oil content were studied at different times in two yam varieties: Diamante 22 and Pico Botella. The experimental data adjusted itself to the first order exponential model for humidity transfer (r > 0.9) for both cultivars. The humidity diffusion coefficient for the two varieties of yam fried at 140°, 160° and 180°C for 1 to 9 minutes were 8.11±0.76, 8.2±0.81, and 8.62 ±0.71*10-9 m2/s for the Diamante 22 variety, respectively, and 8.32±0.82, 8.38±0.78, 8.54±0.84*10-9 m2/s for the Pico de Botella variety. Activation energy was 24.43 kJ/mol for the Diamante 22 variety and 21.27 kJ/mol for the Pico de Botella variety. The results showed that there was higher oil absorption after 180 s and at 140°C while taking into account 0.377 kg water / kg solid moisture loss for Diamond 22 and 0.410 kg water / kg solid Pico de Botella at 180°C for 540 s.

M-Trifluoromethyl-diphenyl diselenide attenuates pentylenetetrazole-induced seizures in mice by inhibiting GABA uptake in cerebral cortex slices

The present study investigated the anticonvulsive effect of the disubstituted diaryl diselenides diphenyl diselenide (PhSe)2, m-trifluoromethyl-diphenyl diselenide (m-CF3-C6H4Se)2, p-chloro-diphenyl diselenide (p-Cl-C6H4Se)2 and p-methoxyl-diphenyl diselenide (p-CH3O-C6H4Se)2 on a chemical model of seizure induced by pentylenetetrazol (PTZ) in mice. (PhSe)2, (p-Cl--C6H4Se)2 and (p-CH3O-C6H4Se)2 did not abolish seizures induced by PTZ in mice. (m-CF3-C6H4Se)2 at the dose of 100mg/kg significantly prolonged the latency of the onset of the first convulsive episode and reduced the number of animals that presented seizures. To investigate the possible mechanisms involved in the anticonvulsant effect of (m-CF3-C6H4Se)2, mice were submitted to different associations (all drugs in a sub-effective dose); aminooxyacetic acid hemihydrochloride (AOAA, a -aminobutyric acid (GABA)-T inhibitor), diazepam (a GABAAreceptor agonist) or DL-2, 4-diamino-n-butyric acid hydrochloride (DABA, an inhibitor of GABA uptake) were pre-administered together with (m-CF3-C6H4Se)2.(m-CF3-C6H4Se)2 + DABA abolished seizures induced by PTZ in mice. (m-CF3-C6H4Se)2 administered alone or with PTZ decreased the levels of GABA uptake in cerebral cortex slices. The present study demonstrates that (m-CF3-C6H4Se)2 exerts anticonvulsant action by decreasing the levels of GABA uptake.

Hypericum perforatum L. (St John's wort) extract Ze 117 inhibits dopamine re‐uptake in rat striatal brain slices. An implication for use in smoking cessation treatment?

Classic synthetic antidepressant drugs, as well as St John's wort extract (SJW), directly inhibit the re-uptake of norepinephrine (NE) and/or serotonin (5-HT) into pre-synaptic axons. With chronic treatment they induce adaptive changes in a number of neurotransmitter receptors in synaptic membranes. The immediate effects of SJW Ze 117, an extract low in hyperforin content, on the specific dopamine (DA) uptake were studied in rat striatal brain slices and compared with the effects on NE and 5-HT uptake in rat cortical brain slices. Specific DA uptake was inhibited in a dose dependent manner. In contrast to the findings in synaptosomal preparations published so far, the extract showed different inhibitory potencies for the respective transporters. The potencies for the uptake inhibition of NA, DA and 5-HT were 30, 7 and 1, respectively. The results indicate that the SJW Ze 117 extract interferes in three ways with the individual uptakes of the relevant neurotransmitters that are considered to be causal in the development of depression. This observation, the concomitant and potent inhibition of DA re-uptake by SJW extract, may additionally provide a rationale for the treatment of nicotine or drug addiction with SJW.

BDNF mediates the neuroprotective effects of positive AMPA receptor modulators against MPP +-induced toxicity in cultured hippocampal and mesencephalic slices

Neurotoxicity is involved in various neurodegenerative diseases including Parkinson's disease (PD), which affects mesencephalic dopaminergic neurons of the substantia nigra (SN). Positive α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor modulators (PARMs, a.k.a. Ampakines, such as CX614) increase brain-derived neurotrophic factor (BDNF) protein levels in vivo and in cultured hippocampal slices. BDNF is a survival factor for various neuronal cell types including mesencephalic dopaminergic neurons. Using cultured mesencephalic and hippocampal slices, we investigated whether preincubation with CX614 could provide neuroprotection against MPP + toxicity and whether such neuroprotection was mediated by BDNF. Various treatment protocols were tested to demonstrate CX614-induced neuroprotection against MPP +. Pretreatment with CX614 significantly reduced MPP +-induced toxicity and increased BDNF levels in both hippocampal and mesencephalic cultured slices; CX614 pretreatment for 6 h in hippocampal slices and 24 h in mesencephalic slices was sufficient to produce significant neuroprotection as assessed with lactate dehydrogenase release in slice medium and propidium iodide uptake in slices. Both a BDNF scavenger and an inhibitor of the BDNF receptor TrkB, abrogated CX614-mediated reduction of MPP +-induced toxicity. Inhibition of Ca 2+-activated proteases, calpains, was also protective against MPP +-induced toxicity. However, co-application of calpain inhibitor with CX614 abolished CX614-mediated protection, suggesting a dual action of calpains in this model. We conclude that CX614 is neuroprotective against MPP +-induced toxicity, an effect mediated by increased BDNF expression and activation of BDNF-dependent signaling pathways. Our results provide support for using PARMs as a new therapy for neurodegenerative disorders, including PD.

Activation of Protein Kinase Cζ Increases OAT1 (SLC22A6)- and OAT3 (SLC22A8)-mediated Transport

Organic anion transporters (OATs) play a pivotal role in the clearance of small organic anions by the kidney, yet little is known about how their activity is regulated. A yeast two-hybrid assay was used to identify putative OAT3-associated proteins in the kidney. Atypical protein kinase Czeta (PKCzeta) was shown to bind to OAT3. Binding was confirmed in immunoprecipitation assays. The OAT3/PKCzeta interaction was investigated in rodent renal cortical slices from fasted animals. Insulin, an upstream activator of PKCzeta, increased both OAT3-mediated uptake of estrone sulfate (ES) and PKCzeta activity. Both effects were abolished by a PKCzeta-specific pseudosubstrate inhibitor. Increased ES transport was not observed in renal slices from OAT3-null mice. Transport of the shared OAT1/OAT3 substrate, rho-aminohippurate, behaved similarly, except that stimulation was reduced, not abolished, in the OAT3-null mice. This suggested that OAT1 activity was also modified by PKCzeta, subsequently confirmed using an OAT1-specific substrate, adefovir. Inhibition of PKCzeta also blocked the increase in ES uptake seen in response to epidermal growth factor and to activation of protein kinase A. Thus, PKCzeta acted downstream of the epidermal growth factor to protein kinase A signaling pathway. Activation of transport was accompanied by an increase in V(max) and was blocked by microtubule disruption, indicating that activation may result from trafficking of OAT3 into the plasma membrane. These data demonstrate that PKCzeta activation up-regulates OAT1 and OAT3 function, and that protein-protein interactions play a central role controlling these two important renal drug transporters.

EUK-207, a superoxide dismutase/catalase mimetic, is neuroprotective against oxygen/glucose deprivation-induced neuronal death in cultured hippocampal slices

EUK-207 is a synthetic superoxide dismutase/catalase mimetic that has been shown to reverse age-related learning deficits and brain oxidative stress in mice. In the present experiments, we tested the effects of EUK-207 on oxygen/glucose deprivation (OGD)-induced cell death in cultured hippocampal slices and on several mechanisms that have been postulated to participate in this process. Cultured hippocampal slices were subjected to 1 h OGD followed by 3 or 24 h recovery in regular medium with glucose and oxygen. Lactate dehydrogenase (LDH) release in culture medium and propidium iodide (PI) uptake in slices were used to evaluate cell viability. When EUK-207 was applied either 1 or 2 h before OGD, OGD-induced LDH release was significantly reduced. When EUK-207 was applied 1 h before OGD and during 24 h recovery, PI uptake was also reduced. OGD-induced accumulation of reactive oxygen species (ROS) was evaluated with the fluorescent probe DCF. DCF fluorescence in slices increased steadily during OGD treatment, rapidly disappeared following return to regular medium before slowly increasing again during the 24 h recovery period. When measured 3 h after OGD, increased ROS levels were significantly reduced by EUK-207. OGD also increased lipid peroxidation levels and this effect was also reduced by EUK-207 6 h following OGD. Cytosolic cytochrome c and nuclear apoptosis-inducing factor (AIF) were increased 3 h after OGD, and the translocation of AIF from mitochondria to nucleus was partly blocked by treatment with EUK-207. In conclusion, EUK-207 provides neuroprotection against OGD-induced cell death in cultured hippocampal slices. As EUK-207 prevents free radical formation and lipid peroxidation, the neuroprotection is related to elimination of free radical generation and lipid peroxidation, as well as to decreased activation of pro-apoptotic factors. Our data support the further clinical evaluation of this class of molecules for the prevention of ischemic cell damage.

The insulin‐regulated aminopeptidase IRAP is colocalised with GLUT4 in the mouse hippocampus – potential role in modulation of glucose uptake in neurones?

It is proposed that insulin-regulated aminopeptidase (IRAP) is the site of action of two peptides, angiotensin IV and LVV-hemorphin 7, which have facilitatory effects on learning and memory. In fat and muscles, IRAP codistributes with the insulin-responsive glucose transporter GLUT4 in specialised vesicles, where it plays a role in the tethering and/or trafficking of these vesicles. This study investigated whether an analogous system exists in two functionally distinct regions of the brain, the hippocampus and the cerebellum. In the hippocampus, IRAP was found in the pyramidal neurones where it exhibited a high degree of colocalisation with GLUT4. Consistent with the role of GLUT4 in insulin-responsive tissues, the glucose transporter was thought to be responsible for facilitating glucose uptake into these pyramidal neurones in response to potassium-induced depolarisation or cAMP activation as the glucose influx was sensitive to indinavir treatment. Angiotensin IV and LVV-hemorphin 7 enhanced this activity-dependent glucose uptake in hippocampal slices. In contrast, in the cerebellum, where the distribution of IRAP was dissociated from GLUT4, the effect of the peptides on glucose uptake was absent. We propose that the modulation of glucose uptake by angiotensin IV and LVV-hemorphin 7 is region-specific and is critically dependent on a high degree of colocalisation between IRAP and GLUT4. These findings also confirm a role for IRAP and GLUT4 in activity-dependent glucose uptake in hippocampal neurones.

GLT‐1 expression and Glu uptake in rat cerebral cortex are increased by phencyclidine

Using western blottings, microdialysis, and functional assays we tested the hypothesis that phencyclidine (PCP) modifies the expression and function of glutamate (Glu) transporters in the rat frontal cortex. Western blotting studies revealed that administration of PCP (10 mg/kg/day; 7 days) increased significantly the expression of the astrocytic Glu transporter GLT-1/EAAT2. Functional studies showed that PCP increased significantly Na+-dependent Glu uptake in slices and in neuron/astrocyte co-cultures, and microdialysis studies evidenced that PCP treatment reduced basal Glu output. In our experimental conditions, PCP did not induce toxicity. These studies show that PCP increases the expression of GLT-1 in the cerebral cortex, thereby increasing Glu uptake and reducing extracellular [Glu].

Blockers of monoamine transporters influence high dopamine concentration uptake in rat brain slices

Blockers of monoamine transporters influence high dopamine concentration uptake in rat brain slices

An organotellurium compound with antioxidant activity against excitotoxic agents without neurotoxic effects in brain of rats

The glutamatergic system is an important target in many neurodegenerative diseases and for several neurotoxic drugs. Organotellurium compounds are often very good free radical scavengers’ agents. Recently, we reported that diethyl-2-phenyl-2-tellurophenyl vinylphosphonate is a compound with low toxicity in vitro and in vivo, as well as also possesses antioxidant activity against iron-induced lipid peroxidation. The aim of this study was to evaluate in vitro the antioxidant and mitochondrial protective effect of this organotellurium compound against quinolinic acid (QA) and sodium nitroprusside (SNP), and to evaluate the in vitro actions of this organotellurium compound in the glutamatergic system in brain of rats. We observed that the telluro vinylphosphonate possess an antioxidant activity against QA and SNP at micromolar concentrations. When tested at antioxidant concentrations (from 2 to 10 μM), the compound does not affect the mitochondrial viability and [ 3H]glutamate uptake in slices from cerebral cortex, hippocampus and striatum, [ 3H]glutamate release from synaptosomal preparations and [ 3H]glutamate binding in membrane preparation. Our data suggest that the telluro vinylphosphonate act as an antioxidant in the central nervous system in vitro with no effects on the glutamatergic system; nevertheless more studies in different models of brain injury must be performed in order to corroborate our findings.

Involvement of Carnitine/organic Cation Transporter OCTN2 (SLC22A5) in Distribution of its Substrate Carnitine to the Heart

This study was designed to clarify the pharmacological role of carnitine/organic cation transporter (Octn) family members in mouse heart. Immunohistochemical analysis revealed that Octn1 was exclusively expressed on endothelial cells in blood vessels. Octn2 was detected on the plasma membrane of cardiac muscle cells by immunoelectron microscopy. Octn3 was not detected in the heart. Integration plot analysis showed that coadministration of unlabeled L-carnitine reduced distribution of L-[3H]carnitine to the heart. L-[3H]Carnitine uptake in heart slices was reduced by carnitine analogs and various Octn2 substrates. L-[3H]Carnitine uptake by heart slices from juvenile visceral steatosis (jvs) mice, which have a hereditary octn2 gene deficiency, was negligible. Distribution of [3H]quinidine, another Octn2 substrate, to the heart was not reduced by L-carnitine, and [3H]quinidine uptake in heart slices was Na(-)-independent and inhibited by cationic drugs, but not carnitine analogs. [3H]Quinidine uptake by heart slices from jvs mice was similar to that of wild-type mice. These results demonstrate that OCTN2 is functionally expressed on the plasma membrane of muscle cells and is involved in distribution of carnitine to the heart. Some mechanism(s) other than OCTN2 is involved in the distribution of quinidine to the heart.

Profile of glutamate uptake and cellular viability in hippocampal slices exposed to oxygen and glucose deprivation: Developmental aspects and protection by guanosine

Stroke syndromes are a major cause of disability in middle and later life resulting in severe neuronal degeneration and loss of brain functions. In situations with energy failure, glutamate transport is impaired and high levels of this amino acid accumulate on the synaptic cleft. Our group has showed that guanosine exerts neuroprotection against neurotoxicity situations. The aim of this work is draw a post-ischemic profile of glutamate uptake and cell damage using an oxygen and glucose deprivation model (OGD) in hippocampal slices from young (P10) and adult (P60) rats, analyzing guanosine effect. OGD decreases glutamate uptake in both ages and recovery times, although decrease in cell viability was only observed 1 and 3 h after OGD in young and adult animals, respectively. Guanosine partially protected cell damage from 1 h in P10 and at 3 h in P60 rats and avoided glutamate uptake decrease from P10 rats at 3 h. The impairment of glutamate transporters since immediately after the insult observed here is probably due to an energetic failure; loss of cell viability was only observed from 1 h after OGD. The mechanism by which guanosine acts in the ‘ischemic’ model used here is still unknown, but evidence leads to its antiapoptotic effect.

Proline promotes decrease in glutamate uptake in slices of cerebral cortex and hippocampus of rats

In the present study we first investigated the in vitro and in vivo effects of proline on glutamate uptake in the cerebral cortex and hippocampus slices of rats. The action of α-tocopherol and/or ascorbic acid on the effects elicited by administration of proline was also evaluated. For in vitro studies, proline (30.0 μM and 1.0 mM) was added to the incubation medium. For acute administration, 29-day-old rats received one subcutaneous injection of proline (18.2 μmol/g body weight) or saline (control) and were sacrificed 1 h later. Results showed that addition of proline in the assay (in vitro studies) reduces glutamate uptake in both cerebral structures. Administration of proline (in vivo studies) reduces glutamate uptake in the cerebral cortex, but not in the hippocampal slices of rats. In another set of experiments, 22-day-old rats were pretreated for one week with daily administration of α-tocopherol (40 mg/kg) or ascorbic acid (100 mg/kg) or with both vitamins. Twelve hours after the last vitamins injection, rats received a single injection of proline or saline and were killed 1 h later. Pretreatment with α-tocopherol and/or ascorbic acid did not prevent the effect of proline administration on glutamate uptake. α-Tocopherol plus ascorbic acid prevented the inhibitory effect of acute hyperprolinemia on Na +,K +-ATPase activity in the cerebral cortex of 29-day-old rats. The data indicate that the effect of proline on reduction of glutamate uptake and Na +,K +-ATPase activity may be, at least in part, involved in the brain dysfunction observed in hyperprolinemic patients.