Protective role of Lycopene against Aroclor 1254-induced changes on GLUT4 in the skeletal muscles of adult male rat

Aroclor 1254 is the commercial mixture of highly toxic environmental pollutant, polychlorinated biphenyls (PCBs). Being immensely durable, it is extensively used and widely distributed. Studies show that Aroclor 1254 causes a variety of adverse health effects through free radical generation. The present investigation was designed to check the effect of Aroclor 1254 on the glucose transporter protein, GLUT4, which plays a key role in glucose homeostasis. The protective role of lycopene against the adverse effect of Aroclor 1254 was also tested. Group 1 rats received corn oil as vehicle and served as control. Groups 2, 3, and 4 were administered with Aroclor 1254 [2?mg kg^?1 body weight (b.w.) day^?1] intraperitoneally for 30 days. Groups 3 and 4 received lycopene (2 and 4?mg kg^?1 b.w. day^?1, respectively) orally in addition to Aroclor 1254. After 30 days, animals were euthanized and the skeletal muscles were dissected to determine the following parameters: GLUT4 messenger RNA (mRNA), GLUT4 protein (both plasma membrane and cytosolic fractions), and ¹⁴C-2-deoxyglucose uptake. Though there was no change in GLUT4 mRNA and fasting plasma glucose levels, Aroclor 1254 significantly decreased the GLUT4 protein level in both the subcellular fractions of the gracilis and triceps muscles. Most important, ¹⁴C-2-deoxyglucose uptake showed a significant decrease in Aroclor 1254 alone treated rats, and Aroclor 1254 plus 4?mg lycopene supplementation treatment maintained the same at par with control. Thus, Aroclor 1254 has adverse effects on GLUT4 translocation and ¹⁴C-2-deoxyglucose uptake, and lycopene administered along with Aroclor 1254 has a protective role over it.     

The role of astroglia in Pb-exposed adult rat brain with respect to glutamate toxicity

Astrocytes maintain neuronal homeostasis in brain and controlling of the released glutamate is one of the most important functions. Since it is suggested that glutamatergic component underlies lead-induced neurotoxic effects and simultaneously, astrocytes serve as a cellular lead (Pb) deposition site, it was of interest to investigate the functioning of astroglia in adult rat brain after short-term exposure to Pb. We examined the expression of main astrocytic glutamate/aspartate transporters--GLAST and GLT-1, which regulate extracellular glutamate concentration. Molecular evidence is provided which indicates overexpression of GLAST mRNA and protein. Simultaneously, decreased expression of GLT-1 mRNA and protein was observed, indicating that of the two glial transporters, GLT-1 is more susceptible to the toxic Pb effect. Protein expression of glutamine synthetase (GS), which converts toxic glutamate to non-toxic glutamine, was doubly enhanced. Moreover, Na+-dependent transport of radioactive glutamine to astroglia-derived fraction was affected in Pb-exposed rats. Both the rate of accumulation and the efflux of amino acid were diminished. Additionally, we observed enhanced expression of glutathione-protein complexes after Pb treatment what suggests activation of S-glutathionylation processes. The results of current studies indicate that lead toxicity in adult rat brain activates astrocytic processes connected with the controlling of glutamate homeostasis. The response of astroglia is rather of neuroprotective character however, downexpression of GLT-1 glutamate transporter and activation of S-glutathionylation processes lead to the question about their significance in Pb-induced neurotoxicity.     

Effects of arsenite on glutamate metabolism in primary cultured astrocytes

The aim of this study was to explore the mechanisms that contribute to neurotoxicity induced by arsenite exposure focusing on the alteration of glutamate metabolism in primary cultured astrocytes. The cells were exposed to 0-30μM arsenite for 24h, and then cell viability, intracellular nonprotein sulfhydryl (NPSH) levels, mitochondrial membrane potential, activity of Na(+)/K(+)-ATPase, glutamine synthetase (GS) and glutamate transporter (GLAST and GLT-1), and protein expression of GS, GLAST and GLT-1 were examined. Compared with those in control, exposure to arsenite resulted in damages of astrocytes in a concentration dependent manner, which were shown by cell viabilities, and supported by morphological observation, mitochondrial membrane potential and intracellular NPSH levels. On the other hand, activities and protein expression of GS, GLAST and GLT-1 were significantly inhibited by arsenite exposure. Moreover, protein expression of GLAST and activities of GS were much more sensitive to arsenite. However, activities of Na(+)/K(+)-ATPase were not influenced obviously by arsenite exposure. In conclusion, findings from this study indicated that exposure to arsenite could inhibit glutamate metabolism in astrocytes, which might be related to arsenic-induced neurotoxicity.     

Nicergoline enhances glutamate uptake via glutamate transporters in rat cortical synaptosomes

To elucidate the mechanisms of neuroprotective action of nicergoline, we examined its effect on glutamate transport in rat cortical synaptosomes and cloned glutamate transporters. In synaptosomes, nicergoline enhanced the glutamate uptake at 1-10 microM in standard medium and suppressed the increase of extracellular glutamate by reversed transport in low Na(+) medium. Apparent increase of extracellular glutamate concentration by dihydrokinate, an inhibitor of glial glutamate transporter GLT-1, was antagonized by nicergoline. In Xenopus oocytes expressing mouse neuronal glutamate transporter (mEAAC1), the glutamate-induced inward current was enhanced by nicergoline. These results suggest that nicergoline reduces the extracellular glutamate concentration through its effect on glutamate transporters.     

Repeated amphetamine treatment causes a persistent elevation of glial fibrillary acidic protein in the caudate-putamen

The ability of repeated D-amphetamine (2 mg/kg) treatment to induce behavioral sensitization in rats and alter glial fibrillary acidic protein (GFAP), dopamine transporter (DAT) and glutamate transporter-1 (GLT-1) immunoreactivities was assessed after a 10-day drug abstinence period. Results showed that a sensitizing regimen of amphetamine caused a persistent increase in the number of GFAP-positive cells in the dorsal and ventral caudate-putamen. DAT and GLT-1 immunoreactivities were unaffected. Although the elevated GFAP expression may be due to a mild neurotoxicity, it is also possible that amphetamine-induced increases in GFAP reflect adaptive changes that may be associated with processes underlying behavioral sensitization.     

Harmine, a natural beta-carboline alkaloid, upregulates astroglial glutamate transporter expression

Glutamate is the predominant excitatory amino acid neurotransmitter in the mammalian central nervous system (CNS). Glutamate transporter EAAT2/GLT-1 is the physiologically dominant astroglial protein that inactivates synaptic glutamate. Previous studies have shown that EAAT2 dysfunction leads to excessive extracellular glutamate and may contribute to various neurological disorders including amyotrophic lateral sclerosis (ALS). The recent discovery of the neuroprotective properties of ceftriaxone, a beta lactam antibiotic, suggested that increasing EAAT2/GLT-1 gene expression might be beneficial in ALS and other neurological/psychiatric disorders by augmenting astrocytic glutamate uptake. Here we report our efforts to develop a new screening assay for identifying compounds that activate EAAT2 gene expression. We generated fetal derived-human immortalized astroglial cells that are stably expressing a firefly luciferase reporter under the control of the human EAAT2 promoter. When screening a library of 1040 FDA approved compounds and natural products, we identified harmine, a naturally occurring beta-carboline alkaloid, as one of the top hits for activating the EAAT2 promoter. We further tested harmine in our in vitro cell culture systems and confirmed its ability to increase EAAT2/GLT1 gene expression and functional glutamate uptake activity. We next tested its efficacy in both wild type animals and in an ALS animal model of disease and demonstrated that harmine effectively increased GLT-1 protein and glutamate transporter activity in vivo. Our studies provide potential novel neurotherapeutics by modulating the activity of glutamate transporters via gene activation. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.     

Embryotoxicity of lead (II) acetate and aroclor 1254 using a new end point of the embryonic stem cell test

We developed a new end point of the mouse stem cell test (EST) for developmental neurotoxicity. We tested 2 developmental neurotoxicants, namely, lead (II) acetate and Aroclor 1254, using this EST. Our results showed that lead (II) acetate is nonembryotoxic, and Aroclor 1254 is weakly embryotoxic. To identify a new end point for developmental neurotoxicity, we used the default method of neuronal differentiation for D3 mouse embryonic stem cells with basic fibroblast growth factor (bFGF) and ascorbic acid. Flow cytometry and real-time polymerase chain reaction were used to quantify the inhibition of neuronal differentiation. Our results showed that both lead (II) acetate and Aroclor 1254 reduced the percentage of microtubule-associated protein 2 (MAP-2)-positive cells and the messenger RNA (mRNA) expression level of MAP-2 in a dose-dependent manner. These results suggested that these methods can be used to develop an additional end point of the EST for developmental neurotoxicity using default differentiation of mouse embryonic stem cells.     

Aroclor 1254, a developmental neurotoxicant, alters energy metabolism- and intracellular signaling-associated protein networks in rat cerebellum and hippocampus

The vast literature on the mode of action of polychlorinated biphenyls (PCBs) indicates that PCBs are a unique model for understanding the mechanisms of toxicity of environmental mixtures of persistent chemicals. PCBs have been shown to adversely affect psychomotor function and learning and memory in humans. Although the molecular mechanisms for PCB effects are unclear, several studies indicate that the disruption of Ca²⁺-mediated signal transduction plays significant roles in PCB-induced developmental neurotoxicity. Culminating events in signal transduction pathways include the regulation of gene and protein expression, which affects the growth and function of the nervous system. Our previous studies showed changes in gene expression related to signal transduction and neuronal growth. In this study, protein expression following developmental exposure to PCB is examined. Pregnant rats (Long Evans) were dosed with 0.0 or 6.0 mg/kg/day of Aroclor-1254 from gestation day 6 through postnatal day (PND) 21, and the cerebellum and hippocampus from PND14 animals were analyzed to determine Aroclor 1254-induced differential protein expression. Two proteins were found to be differentially expressed in the cerebellum following PCB exposure while 18 proteins were differentially expressed in the hippocampus. These proteins are related to energy metabolism in mitochondria (ATP synthase, sub unit β (ATP5B), creatine kinase, and malate dehydrogenase), calcium signaling (voltage-dependent anion-selective channel protein 1 (VDAC1) and ryanodine receptor type II (RyR2)), and growth of the nervous system (dihydropyrimidinase-related protein 4 (DPYSL4), valosin-containing protein (VCP)). Results suggest that Aroclor 1254-like persistent chemicals may alter energy metabolism and intracellular signaling, which might result in developmental neurotoxicity.     

Inhibition of tetanically sciatic stimulation-induced LTP of spinal neurons and Fos expression by disrupting glutamate transporter GLT-1

Tetanic stimulation of the sciatic nerve produces spinal long-term potentiation (LTP) of C-fiber evoked field potentials, which is NMDA dependent and may be the substrate of inflammation- or nerve injury-produced central sensitization. Glial glutamate transporter GLT-1 has been considered as an important regulator of excitatory synaptic transmission and nociception. In the present study, we investigated the effects of GLT-1 on the spinal LTP and Fos expression induced by tetanically sciatic stimulation. Intrathecal administration of dihydrokainate (DHK), a GLT-1 selective inhibitor, partially inhibited (0.1 mM) or completely blocked (3.0 mM) the spinal LTP, which may be related to an accumulation of extracellular glutamate. Intrathecal DHK (3.0 mM) also suppressed tetanic stimulation-induced spinal Fos expression. Double immunofluorescence showed no Fos expression in glial fibrillary acidic protein (GFAP)-positive cells, and the cell DNA fragment study failed to detect a significant apoptosis of spinal neurons. These results suggest that disruption of GLT-1 may be associated with the inhibition of functional activation of spinal neurons expressing Fos, but not with glutamate excitotoxicity. In conclusion, glial GLT-1 may play an important role in tetanically sciatic stimulation-induced LTP of spinal nociceptive neurons via the regulation of extracellular levels of glutamate to an appropriate concentration.     

Beta-lactam antibiotic prevents tolerance to the hypothermic effect of a kappa opioid receptor agonist

Beta-lactam antibiotics are the only clinically approved drugs which directly increase glutamate uptake. They activate the glutamate transporter subtype 1 (GLT-1), the protein responsible for 90% of glutamate uptake in the mammalian brain. The capacity of GLT-1 to clear extracellular glutamate suggests that glutamate transporter activators be explored for therapeutic approaches to clinical conditions caused by increased glutamatergic transmission. One of the most common drug effects mediated by increased glutamatergic signaling is opioid tolerance. Therefore, we tested the hypothesis that a beta-lactam antibiotic (ceftriaxone), by increasing glutamate uptake, prevents tolerance to hypothermia induced by a kappa opioid receptor agonist (U-50,488H). A single injection of U-50,488H (20mg/kg, s.c.) caused significant hypothermia in rats. Tolerance to the hypothermic effect of U50,488H was induced by injecting U50,488H (20mg/kg) twice daily for 7days. Pretreatment with ceftriaxone (200mg/kg, i.p.) for 7days did not alter the acute hypothermic response to U50,488H (20mg/kg) but did prevent tolerance to U50,488H-induced hypothermia. Central administration of dl-threo-beta-benzyloxyaspartic acid (TBOA) (0.2mumol, i.c.v.), a glutamate transporter inhibitor, abolished the effect of ceftriaxone. These results identify a functional interaction between ceftriaxone and U50,488H in vivo and provide pharmacological evidence that a beta-lactam antibiotic abolishes tolerance to hypothermia induced by a kappa opioid receptor agonist.     

谷氨酸转运体亚型谷氨酸转运体1与其调控药物的研究进展

胞外谷氨酸浓度的动态平衡是由谷氨酸转运体精确调控的,谷氨酸转运体功能或表达失调时导致胞外谷氨酸水平异常,引起一系列神经系统疾病。其中谷氨酸转运体1(GLT-1)起着"谷氨酸泵"作用,近年来还发现了仅在肽链C末端发生改变的GLT-1剪切变异体;其中GLT-1a、GLT-1b和GLT-1v发现与某些疾病具有相关性。药物调控谷氨酸转运体的表达或功能,维持胞外谷氨酸正常浓度,能有效改善病理状况。目前已有多种药物被报道对谷氨酸转运体具有激动或抑制作用,如能够上调GLT-1活性的药物有头孢曲松、苯环己哌啶、胞二磷胆碱、利鲁唑、凝血酶、蛋白激酶B等;下调GLT-1活性的药物有依托咪酯、氯氮平、天冬酰胺类衍生物、内皮素等。该文将调控谷氨酸转运体的药物做一总结,为药物开发和临床治疗提供新的思路。     

Heme-oxygenase-1 promotes polychlorinated biphenyl mixture aroclor 1254-induced oxidative stress and dopaminergic cell injury.

Dopaminergic (DAergic) systems have been identified as putative targets for polycholorinated biphenyl (PCB) actions. However, the precise mechanisms leading to neurotoxicity are unresolved. Reactive oxygen species (ROS) were recently shown to mediate injury in DAergic MN9D cells following exposure to Aroclor 1254 (A1254), a commercial PCB mixture. The oxidative stress response in DAergic cells included a persistent expression of heme oxygenase-1 (HO-1). This study tested the hypothesis that a sustained PCB-induced HO-1 response leads to abnormally high Fe levels, which generates ROS production and mediates death in the MN9D DAergic cell model. Accordingly, results indicated that A1254 augmented intracellular Fe levels in MN9D cells after 24 h. Fe chelation by desferoxamine or pharmacologic inhibition of HO activity with tin-protoporphyrin reduced Fe accumulation, ROS production, and cytotoxicity following A1254 exposure. HO-1 over-expression predisposed MN9D DAergic cells to enhanced ROS production and cell death in response to PCBs. Conversely, antisense inhibition of HO-1 expression prevented PCB-induced ROS production and cell death. These observations suggest that enhanced HO-1 catalytic activity and subsequent liberation of Fe participate in neurotoxic DAergic cell injury caused by A1254 exposure in vitro.     

Differential in vitro neurotoxicity of the flame retardant PBDE-99 and of the PCB Aroclor 1254 in human astrocytoma cells

Polybrominated diphenyl ethers (PBDEs) are an important class of flame retardants. Because of their presence in maternal milk and their structural similarity to polychlorinated biphenyls (PCBs), concern has been raised on their possible developmental neurotoxicity. Aim of the present study was to investigate the in vitro effects of PBDE-99 (2,2', 4,4', 5-pentabromodiphenyl ether) on astroglial cells (human 132-1N1 astrocytoma cells) and comparing it with those of the PCB mixture Aroclor 1254. Both PBDE-99 and Aroclor 1254 caused a concentration-dependent inhibition of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) reduction, however, only the latter increased lactate dehydrogenase (LDH) release or cell death, assessed by the trypan blue assay. PBDE-99 caused translocation of the three protein kinase C (PKC) isozymes (alpha, epsilon, zeta) present in 132-1N1 astrocytoma cells, while Aroclor 1254 affected only PKCalpha and epsilon translocation. However, pre-incubation with the PKC inhibitor GF109203X or PKC down-regulation by the phorbol ester PMA, had minimal or no effect on PBDE-99 or Aroclor 1254-induced cytotoxicity. Similarly, the calcium chelator BAPTA-AM, the tyrosine kinase inhibitor genistein, and the MEK (mitogen activated protein kinase kinase) inhibitor PD98059 had no effect on PBDE-99 and Aroclor 1254 cytoxicity. On the other hand, the phosphatidylinositol 3 kinase (PI-3K) inhibitor LY290042 enhanced PBDE-99 toxicity, but did not affect Aroclor 1254. Because of the involvement of PI-3K in apoptotic cell death, the ability of PBDE-99 and Aroclor 1254 to induce apoptosis in astrocytoma cells was investigated. PBDE-99, but not Aroclor 1254, caused apoptotic cell death in astrocytoma cells, assessed by the TUNEL method and by Hoechst 33258 staining, via a p53 dependent mechanism. These results suggest that PBDE-99 and Aroclor 1254 exert differential cytotoxic effects on human astroglial cells.     

The neuroprotective agent MS-153 stimulates glutamate uptake

We investigated the effect of (R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153), a novel neuroprotective agent, on L-[3H]glutamate uptake through GLT-1, a Na(+)/K(+)-dependent glial glutamate transporter, expressed in COS-7 cells. MS-153 (1-100 microM) accelerated the L-[3H]glutamate uptake through GLT-1 in a concentration-dependent and time-dependent manner. Eadie-Hofstee analysis revealed that MS-153 significantly decreased the K(m) of the glutamate uptake by COS-7 cells expressing GLT-1. In contrast, [3H]gamma-aminobutyric acid (GABA) uptake through a glial GABA transporter was not affected. In addition, MS-153 increased Na(+) currents through GLT-1 expressed in Xenopus oocytes. We also investigated the effect of MS-153 on amino acid efflux from rat hippocampal slices. The increase in glutamate efflux induced by 50 mM KCl was significantly attenuated by the treatment with MS-153 at 10 microM, while MS-153 had no significant effect on the K(+)-evoked efflux of GABA. Furthermore, the increase in glutamate efflux by ischemia (hypoxia/aglycemia) was partially, but significantly inhibited by MS-153. These results suggest that the cerebroprotective effect of MS-153 in this ischemic model in vivo is due to the specific reduction of the glutamate concentration in the extracellular space, which can probably be attributed to the acceleration of glutamate uptake by the indirect modulation of the glutamate transporter activity.     

谷氨酸转运体、谷氨酸/胱氨酸转运体与谷氨酸神经细胞毒作用

谷氨酸转运体与谷氨酸／胱氨酸转运体在脑缺血疾病中起重要作用，谷氨酸转运体的结构或功能改变可使细胞间隙的谷氨酸浓度急剧升高，激活NMDA受体产生一系列的表现，同时抑制谷氨酸／胱氨酸转运体对胱氨酸的摄取，介导谷胱苷肽耗竭、氧自由基升高、胞内钙升高、线粒体损伤、细胞色素c释放等神经细胞毒环节，激活半胱天冬酶诱导凋亡。可进一步加重谷氨酸的神经细胞毒作用。     

Involvement of glial glutamate transporters in morphine dependence and naloxone-precipitated withdrawal

A body of evidence supports that excitatory amino acid systems, particularly glutamatergic one, participate in morphine dependence and naloxone-precipitated withdrawal. In this study, we examined the involvement of glial glutamate transporters, GLT-1 and GLAST, in them. Rats were rendered morphine-dependent by subcutaneous implantation of two 75 mg morphine pellets for 5 days. Intracerebroventricular administration of DL-threo-beta-benzyloxyaspartate, a glutamate transporter inhibitor significantly facilitated various naloxone-precipitated withdrawal signs. By northern blot analysis, the expression of GLT-1 mRNA was found to decrease significantly in the striatum and thalamus of morphine-dependent rats, and to increase significantly in the striatum 2 hr after the naloxone-precipitated withdrawal. On the other hand, there were no significant changes in GLAST mRNA levels in any brain regions. In vivo microdialysis experiments revealed that the extracellular glutamate levels was elevated in the striatum and nucleus accumbens, in which the changes of GLT-1 mRNA level were observed, during naloxone-precipitated morphine withdrawal. In cultured astrocytes, the expression of GLT-1 mRNA was regulated by agents activating the cAMP pathway, as well as beta-adrenergic agonist and dopamine, but not morphine. These results suggest that the changes of GLT-1 expression, which alter the glutamate uptake and affect the glutamatergic transmission efficiency, play a role in the development of morphine dependence and the expression of morphine withdrawal.     

Manganese inhalation by rhesus monkeys is associated with brain regional changes in biomarkers of neurotoxicity.

The purpose of this study was to evaluate biochemical markers of neurotoxicity following subchronic manganese sulfate (MnSO(4)) inhalation. Juvenile rhesus monkeys were exposed to MnSO(4) at 0, 0.06, 0.3, or 1.5 mg Mn/m(3) for 65 days. Glutamine synthetase (GS), glutamate transporters (glutamate transporter-1 [GLT-1] and glutamate/aspartate transporter [GLAST]) and tyrosine hydroxylase (TH) protein levels, metallothionein (MT), GLT-1, GLAST, TH and GS mRNA levels, and total glutathione (GSH) levels were assessed in known targets (caudate, globus pallidus, putamen) as well as the cerebellum, frontal cortex, and olfactory cortex. All MnSO(4)-exposed monkeys had decreased pallidal GS protein, decreased caudate GLT-1 mRNA, decreased pallidal GLAST protein, and increased olfactory cortical TH mRNA levels. Monkeys exposed to MnSO(4) at 0.06 or 0.3 mg Mn/m(3) had significantly increased pallidal mRNA levels for GLT-1, GLAST, and TH. Monkeys exposed to MnSO(4) at > or = 0.3 mg Mn/m(3) had several alterations including decreased frontal cortical MT mRNA, decreased caudate, globus pallidus, olfactory cortex, and cerebellum GLT-1 protein, decreased olfactory cortex and cerebellum GLAST protein, increased cerebellar GLAST mRNA, and decreased pallidal TH protein levels. Lastly, GSH levels were significantly increased in the frontal cortex and decreased in the caudate of monkeys exposed to the 1.5-mg Mn/m(3) compared to the controls. Overall, as in our previous studies, we observed that increased Mn concentrations due to airborne Mn exposure differentially affects biomarkers in each brain region (e.g., GSH was increased in the frontal cortex and decreased in the caudate despite two- to threefold increases in Mn concentrations in these regions).     

Blockade of Astrocytic Glutamate Uptake in the Prefrontal Cortex Induces Anhedonia

Major depression is associated with both dysregulated glutamatergic neurotransmission and fewer astrocytes in limbic areas including the prefrontal cortex (PFC). These deficits may be functionally related. Notably, astrocytes regulate glutamate levels by removing glutamate from the synapse via the glutamate transporter (GLT-1). Previously, we demonstrated that central blockade of GLT-1 induces anhedonia and c-Fos expression in the PFC. Given the role of the PFC in regulating mood, we hypothesized that GLT-1 blockade in the PFC alone would be sufficient to induce anhedonia in rats. We microinjected the GLT-1 inhibitor, dihydrokainic acid (DHK), into the PFC and examined the effects on mood using intracranial self-stimulation (ICSS). At lower doses, intra-PFC DHK produced modest increases in ICSS thresholds, reflecting a depressive-like effect. At higher doses, intra-PFC DHK resulted in cessation of responding. We conducted further tests to clarify whether this total cessation of responding was related to an anhedonic state (tested by sucrose intake), a nonspecific result of motor impairment (measured by the tape test), or seizure activity (measured with electroencephalogram (EEG)). The highest dose of DHK increased latency to begin drinking without altering total sucrose intake. Furthermore, neither motor impairment nor evidence of seizure activity was observed in the tape test or EEG recordings. A decrease in reward value followed by complete cessation of ICSS responding suggests an anhedonic-like effect of intra-PFC DHK; a conclusion that was substantiated by an increased latency to begin sucrose drinking. Overall, these results suggest that blockade of astrocytic glutamate uptake in the PFC is sufficient to produce anhedonia, a core symptom of depression.