The effect of mental fatigue on the performance of Australian football specific skills amongst amateur athletes.

OBJECTIVES: This study investigated the effects of induced mental fatigue on the performance of Australian football (AF) specific skills amongst amateur AF players. DESIGN: Randomised cross over trial. METHODS: Twenty-five amateur AF players performed a series of standardised tests from the Australian Football League (AFL) Draft Combine after completing a 30-min Stroop test (mental fatigue condition) or 30-min control condition. The AFL Draft Combine tests included the standing vertical jump test, running vertical jump test, agility test, 20m sprint, Matthew Lloyd clean hands test, Brad Johnson goal kicking test and a Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IR1) test. RESULTS: The Stroop test score decreased during the Stroop test (first five trials: mean=84.7, SD=3.5; last five trials: mean=82.2, SD=5.0, p=0.03). The Yo-Yo IR1 test (mental fatigue: median=920m, IQR=400; control: median=1040m, IQR=760; p=0.03) and Brad Johnson goalkicking test (mental fatigue: median=19.0, IQR=5.0; control: median=25.0, IQR=10.0, p=0.048) were negatively affected by mental fatigue. No other Draft Combine tests demonstrated a negative affect from mental fatigue. CONCLUSIONS: Mental fatigue had a detrimental influence on the performance of AF specific skills. The findings may have implications for AF players who are required to sustain attention and concentration for prolonged periods before and during matches.

Movement responses to environment: fast inference of variation among southern elephant seals with a mixed effects model.

Like many species, movement patterns of southern elephant seals (Mirounga leonina) are being influenced by long-term environmental change. These seals migrate up to 4,000 km from their breeding colonies, foraging for months in a variety of Southern Ocean habitats. Understanding how movement patterns vary with environmental features and how these relationships differ among individuals employing different foraging strategies can provide insight into foraging performance at a population level. We apply new fast-estimation tools to fit mixed effects within a random walk movement model, rapidly inferring among-individual variability in southern elephant seal environment-movement relationships. We found that seals making foraging trips to the sea ice on or near the Antarctic continental shelf consistently reduced speed and directionality (move persistence) with increasing sea-ice coverage but had variable responses to chlorophyll a concentration, whereas seals foraging in the open ocean reduced move persistence in regions where circumpolar deep water shoaled. Given future climate scenarios, open-ocean foragers may encounter more productive habitat but sea-ice foragers may see reduced habitat availability. Our approach is scalable to large telemetry data sets and allows flexible combinations of mixed effects to be evaluated via model selection, thereby illuminating the ecological context of animal movements that underlie habitat usage.

Genetic relatedness reveals total population size of white sharks in eastern Australia and New Zealand.

Conservation concerns exist for many sharks but robust estimates of abundance are often lacking. Improving population status is a performance measure for species under conservation or recovery plans, yet the lack of data permitting estimation of population size means the efficacy of management actions can be difficult to assess, and achieving the goal of removing species from conservation listing challenging. For potentially dangerous species, like the white shark, balancing conservation and public safety demands is politically and socially complex, often leading to vigorous debate about their population status. This increases the need for robust information to inform policy decisions. We developed a novel method for estimating the total abundance of white sharks in eastern Australia and New Zealand using the genetic-relatedness of juveniles and applying a close-kin mark-recapture framework and demographic model. Estimated numbers of adults are small (ca. 280-650), as is total population size (ca. 2,500-6,750). However, estimates of survival probability are high for adults (over 90%), and fairly high for juveniles (around 73%). This represents the first direct estimate of total white shark abundance and survival calculated from data across both the spatial and temporal life-history of the animal and provides a pathway to estimate population trend.

Ketamine anesthesia during the first week of life can cause long-lasting cognitive deficits in rhesus monkeys.

Previously our laboratory has shown that ketamine exposure (24h of clinically relevant anesthesia) causes significant increases in neuronal cell death in perinatal rhesus monkeys. Sensitivity to this ketamine-induced neurotoxicity was observed on gestational days 120-123 (in utero exposure via maternal anesthesia) and on postnatal days (PNDs) 5-6, but not on PNDs 35-37. In the present study, six monkeys were exposed on PND 5 or 6 to intravenous ketamine anesthesia to maintain a light surgical plane for 24h and six control animals were unexposed. At 7 months of age all animals were weaned and began training to perform a series of cognitive function tasks as part of the National Center for Toxicological Research (NCTR) Operant Test Battery (OTB). The OTB tasks used here included those for assessing aspects of learning, motivation, color discrimination, and short-term memory. Subjects responded for banana-flavored food pellets by pressing response levers and press-plates during daily (M-F) test sessions (50 min) and were assigned training scores based upon their individual performance. As reported earlier (Paule et al., 2009) beginning around 10 months of age, control animals significantly outperformed (had higher training scores than) ketamine-exposed animals for approximately the next 10 months. For animals now over 3 and one-half years of age, the cognitive impairments continue to manifest in the ketamine-exposed group as poorer performance in the OTB learning and color and position discrimination tasks, as deficits in accuracy of task performance, but also in response speed. There are also apparent differences in the motivation of these animals which may be impacting OTB performance. These observations demonstrate that a single 24-h episode of ketamine anesthesia, occurring during a sensitive period of brain development, results in very long-lasting deficits in brain function in primates and provide proof-of-concept that general anesthesia during critical periods of brain development can result in subsequent functional deficits. Supported by NICHD, CDER/FDA and NCTR/FDA.

Changes in gene expression after phencyclidine administration in developing rats: a potential animal model for schizophrenia.

Repeated administration of phencyclidine (PCP), an N-methyl-d-aspartate (NMDA) receptor antagonist, during development, may result in neuronal damage that leads to behavioral deficits in adulthood. The present study examined the potential neurotoxic effects of PCP exposure (10mg/kg) in rats on postnatal days (PNDs) 7, 9 and 11 and the possible underlying mechanism(s) for neurotoxicity. Brain tissue was harvested for RNA extraction and morphological assessments. RNA was collected from the frontal cortex for DNA microarray analysis and quantitative RT-PCR. Gene expression profiling was determined using Illumina Rat Ref-12 Expression BeadChips containing 22,226 probes. Based on criteria of a fold-change greater than 1.4 and a P-value less than 0.05, 19 genes including NMDAR1 (N-methyl-d-aspartate receptor) and four pro-apoptotic genes were up-regulated, and 25 genes including four anti-apoptotic genes were down-regulated, in the PCP-treated group. In addition, the schizophrenia-relevant genes, Bdnf (Brain-derived neurotrophic factor) and Bhlhb2 (basic helix-loop-helix domain containing, class B, 2), were significantly different between the PCP and the control groups. Quantitative RT-PCR confirmed the microarray results. Elevated neuronal cell death was further confirmed using Fluoro-Jade C staining. These findings support the hypothesis that neurodegeneration caused by PCP occurs, at least in part, through the up-regulation of NMDA receptors, which makes neurons possessing these receptors more vulnerable to endogenous glutamate. The changes in schizophrenia-relevant genes after repeated PCP exposure during development may provide important information concerning the validation of an animal model for this disorder.

An acute dose of gamma-hydroxybutyric acid alters gene expression in multiple mouse brain regions.

Gamma-hydroxybutyric acid (GHB) is normally found in the brain in low concentrations and may function as a neurotransmitter, although the mechanism of action has not been completely elucidated. GHB has been used as a general anesthetic and is currently used to treat narcolepsy and alcoholism. Recreational use of GHB is primarily as a "club drug" and a "date rape drug," due to its amnesic effects. For this study, the hypothesis was that behavioral and neurochemical alterations may parallel gene expression changes in the brain after GHB administration. Adult male C57/B6N mice (n=5/group) were administered a single dose of 500 mg/kg GHB (i.p.) and were sacrificed 1, 2 and 4 h after treatment. Control mice were administered saline. Brains were removed and regionally dissected on ice. Total RNA from the hippocampus, cortex and striatum was extracted, amplified and labeled. Gene expression was evaluated using Agilent whole mouse genome 4x44K oligonucleotide microarrays. Microarray data were analyzed by ArrayTrack and differentially expressed genes (DEGs) were identified using P < or = 0.01 and a fold change > or = 1.7 as the criteria for significance. Principal component analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that samples from each time point clustered into distinct treatment groups with respect to sacrifice time. Ingenuity pathways analysis (IPA) was used to identify involved pathways. The results show that GHB induces gene expression alterations in hundreds of genes in the hippocampus, cortex and striatum, and the number of affected genes increases throughout a 4-h time course. Many of these DEGs are involved in neurological disease, apoptosis, and oxidative stress.

Gene expression profiling in the developing rat brain exposed to ketamine.

Ketamine, a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, is associated with accelerated neuronal apoptosis in the developing rodent brain. In this study, postnatal day (PND) 7 rats were treated with 20 mg/kg ketamine or saline in six successive doses (s.c.) at 2-h intervals. Brain frontal cortical areas were collected 6 h after the last dose and RNA isolated and hybridized to Illumina Rat Ref-12 Expression BeadChips containing 22,226 probes. Many of the differentially expressed genes were associated with cell death or differentiation and receptor activity. Ingenuity Pathway Analysis software identified perturbations in NMDA-type glutamate, GABA and dopamine receptor signaling. Quantitative polymerase chain reaction (Q-PCR) confirmed that NMDA receptor subunits were significantly up-regulated. Up-regulation of NMDA receptor mRNA signaling was further confirmed by in situ hybridization. These observations support our working hypothesis that prolonged ketamine exposure produces up-regulation of NMDA receptors and subsequent over-stimulation of the glutamatergic system by endogenous glutamate, triggering enhanced apoptosis in developing neurons.

Expression of genes related to oxidative stress in the mouse brain after exposure to silver-25 nanoparticles.

Nanoparticles are small scale substances (<100 nm) used in biomedical applications, electronics, and energy production. Increased exposure to nanoparticles being produced in large-scale industry facilities elicits concerns for the toxicity of certain classes of nanoparticles. This study evaluated the effects of silver-25 nm (Ag-25) nanoparticles on gene expression in different regions of the mouse brain. Adult-male C57BL/6N mice were administered (i.p.) 100mg/kg, 500 mg/kg or 1,000 mg/kg Ag-25 and sacrificed after 24h. Regions from the brain were rapidly removed and dissected into caudate nucleus, frontal cortex and hippocampus. Total RNA was isolated from each of the three brain regions collected and real-time RT-PCR analysis was performed using Mouse Oxidative Stress and Antioxidant Defense Arrays. Array data revealed the expression of genes varied in the caudate nucleus, frontal cortex and hippocampus of mice when treated with Ag-25. The data suggest that Ag-25 nanoparticles may produce neurotoxicity by generating free radical-induced oxidative stress and by altering gene expression, producing apoptosis and neurotoxicity.

The effects of L-carnitine on the combination of, inhalation anesthetic-induced developmental, neuronal apoptosis in the rat frontal cortex.

The anesthetic gas nitrous oxide (N2O) and the volatile anesthetic isoflurane (ISO) are commonly used in surgical procedures for human infants and in veterinary and laboratory animal practice to produce loss of consciousness and analgesia. Recent reports indicate that exposure of the developing brain to general anesthetics that block N-methyl-D-aspartate (NMDA) glutamate receptors or potentiate GABA(A) receptors can trigger widespread apoptotic neurodegeneration. In the present study, the question arises whether a relatively low dose of ISO alone or its combination with N2O entails significant risk of inducing enhanced apoptosis. In addition, the role of L-carnitine to attenuate these effects was also examined. Postnatal day 7 (PND-7) rat pups were exposed to N2O (75%) or a low dose of ISO (0.55%) alone, or N2O plus ISO for 2, 4, 6 or 8 h with or without L-carnitine. The neurotoxic effects were evaluated 6 h after completion of anesthetic administration. No significant neurotoxic effects were observed for the animals exposed to N2O or ISO alone. However, enhanced apoptotic cell death was apparent when N2O was combined with ISO at exposure durations of 6 h or more. Co-administration of L-carnitine (300 or 500 mg/kg, i.p.) effectively protected neurons from the anesthetic-induced damage. These data indicate that 6 h or more of inhaled anesthetic exposure consisting of a combination of N2O and ISO results in enhanced neuronal apoptosis, and L-carnitine effectively blocks the neuronal apoptosis caused by inhalation anesthetics in the developing rat brain.

L-carnitine protects neurons from 1-methyl-4-phenylpyridinium-induced neuronal apoptosis in rat forebrain culture.

1-Methyl-4-phenylpyridinium ion (MPP+), an inhibitor of mitochondrial complex I, has been widely used as a neurotoxin because it elicits a severe Parkinson's disease-like syndrome with an elevation of intracellular reactive oxygen species (ROS) and apoptosis. L-carnitine plays an integral role in attenuating the brain injury associated with mitochondrial neurodegenerative disorders. The present study investigates the effects of L-carnitine against the toxicity of MPP+ in rat forebrain primary cultures. Cells in culture were treated for 24 h with 100, 250, 500 and 1000 microM MPP+ alone or co-incubated with L-carnitine. MPP+ produced a dose-related increase in DNA fragmentation as measured by cell death ELISA (enzyme-linked immunosorbent assay), an increase in the number of TUNEL (terminal dUTP nick-end labeling)-positive cells and a reduction in the mitochondrial metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). No significant effect was observed with the release of lactate dehydrogenase (LDH), indicating that cell death presumably occurred via apoptotic mechanisms. Co-incubation of MPP+ with L-carnitine significantly reduced MPP+-induced apoptosis. Western blot analyses showed that neurotoxic concentrations of MPP+ decreased the ratio of BCL-X(L) to Bax and decreased the protein levels of polysialic acid neural cell adhesion molecules (PSA-NCAM), a neuron specific marker. L-carnitine blocked these effects of MPP+ suggesting its potential therapeutic utility in degenerative disorders such as Parkinson's disease, Alzheimer's disease, ornithine transcarbamylase deficiency and other mitochondrial diseases.

Selective alterations of transcription factors in MPP+-induced neurotoxicity in PC12 cells.

MPP(+) (1-methyl-4-phenylpyridinium; the active metabolite of the neurotoxin MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine)) depletes dopamine (DA) content and elicits cell death in PC12 cells. However, the mechanism of MPP(+)-induced neurotoxicity is still unclear. In this study, the dose response and time-course of MPP(+)-induced DA depletion and decreased cell viability were determined in nerve growth factor (NGF)-differentiated PC12 cells. The alteration of transcription factors (TFs) induced by MPP(+) from a selected dose level and time point was then evaluated using protein/DNA-binding arrays. K-means clustering analysis identified four patterns of protein/DNA-binding changes. Three of the 28 TFs identified in PC12 cells increased by 100% (p53, PRE, Smad SBE) and 2 decreased by 50% (HSE, RXR(DR1)) of control with MPP(+) treatment. In addition, three TFs decreased within the range of 33-50% (TFIID, E2F1, CREB) and two TFs increased within the range of 50-100% (PAX-5, Stat4). An electrophoretic mobility shift assay (EMSA) was used to confirm the changes of p53 and HSE. The observed changes in TFs correlated with the alterations of DA and cell viability. The data indicates that selective transcription factors are involved in MPP(+)-induced neurotoxicity and it provides mechanistic information that may be applicable to animal studies with MPTP and clinical studies of Parkinson's disease.

Quantitative exposure assessment: application of physiologically-based pharmacokinetic (PBPK) modeling of low-dose, long-term exposures of organic acid toxicant in the brain.

Our objective was to construct a physiologically-based pharmacokinetic (PBPK) model describing the kinetic behavior of 2,4-dichlorophenoxyacetic acid (2,4-D) on rats after long-term exposures to low doses. Our study demonstrated the model's ability to simulate uptake of 2,4-D in discrete areas of the rat brain. The model was derived from the generic PBPK model that was first developed for high-dose, single exposures of 2,4-D to rats or rabbits (Kim, C.S., Gargas, M.L., Andersen, M.E., 1994. Pharmacokinetic modeling of 2,4-dichlorophenoxyacetic acid (2,4-D) in rats and rabbits brain following single dose administration. Toxicol. Lett. 74, 189-201; Kim, C.S., Slikker, W., Jr., Binienda, Z., Gargas, M.L., Andersen, M.E., 1995. Development of a physiologically based pharmacokinetic (PBPK) model for 2,4-dichlorophenoxyacetic acid (2,4-D) dosimetry in discrete areas of the brain following a single intraperitoneal or intravenous dose. Neurotox. Teratol. 17, 111-120.), to which a subcutaneous (hypodermal) compartment was incorporated for low-dose, long-term infusion. It consisted of two body compartments, along with compartments for venous and arterial blood, cerebrospinal fluid, brain plasma and six brain regions. Uptake of the toxin was membrane-limited by the blood-brain barrier with clearance from the brain provided by cerebrospinal fluid 'sink' mechanisms. This model predicted profiles of 2,4-D levels in brain and blood over a 28-day period that compared well with concentrations measured in vivo with rats that had been given 2,4-D (1 or 10 mg/kg per day) with [14C]-2,4-D subcutaneously (s.c.) for 7, 14, or 28 days, respectively. This PBPK model should be an effective tool for evaluating the target tissue doses that may produce the neurotoxicity of organic acid toxicants after low-dose, long-term exposures to contaminated foods or the environment.

Transplacental pharmacokinetics and fetal distribution of 2', 3'-didehydro-3'-deoxythymidine (d4T) and its metabolites in late-term rhesus macaques.

BACKGROUND: The overall goal of human immunodeficiency virus (HIV) therapy during pregnancy is to maintain maternal health and reduce the probability of vertical transmission during gestation and delivery, while keeping toxicity risks low. Azidothymidine (AZT) is currently recommended for pregnant women infected with HIV; however, many pregnant women are unable to tolerate AZT because of toxicity. In the present study, the placental transfer and fetal accumulation of the anti-HIV compound 2',3'-didehydro-3'-deoxythymidine (d4T) and its active (triphosphorylated) and inactive (thymine and beta-aminoisobutyric acid) metabolites were examined at steady state in late-term rhesus macaques. METHODS: On the day of the hysterotomy, the mother was administered an intravenous loading dose of d4T, followed by a 3-hr steady-state intravenous infusion that also included [(3)H]d4T as a tracer. After 3 hr of infusion, the fetus was delivered by cesarean section under halothane/N(2)O anesthesia. Plasma, amniotic fluid, and tissues were analyzed for d4T and its inactive metabolites by HPLC; tissue samples were analyzed for d4T and active (phosphorylated) metabolites by strong anion-exchange HPLC. RESULTS: Maternal steady-state plasma concentrations of d4T were 1-2 microg/ml, with a fetal-to-maternal plasma ratio of 0.85 +/- 0.09. The fetal tissue distribution of radioactivity was highest in the kidney and lowest in the brain. D4T, thymine, and beta-aminoisobutyric acid were detected in all fetal tissues examined. CONCLUSIONS: Our data indicate that d4T readily crosses the placenta and is present in the fetus as parent compound or its inactive metabolites after maternal infusion. Although fetal plasma concentrations of d4T were similar to clinical d4T concentrations, no phosphorylated metabolites were detected. Teratology 62:93-99, 2000. Published 2000 Wiley-Liss, Inc.

Temporal development of 2',3'-dideoxyinosine (ddI)-induced peripheral myelinopathy.

The anti-HIV therapeutic dideoxyinosine (ddI) has been reported to produce a painful, dose-limiting peripheral myelinopathy in HIV-infected patients after chronic administration. We have previously demonstrated ddI-induced myelinopathy in a non-HIV-infected rat model after 20 weeks of dosing, characterized by myelin splitting and intramyelin edema. The present study examined the time course needed to produce the ddI-induced neuropathy. Adult male Sprague-Dawley rats were gavaged with vehicle or 415 mg/kg ddI twice daily for up to 20 weeks. Groups of treated (n = 6-8) and control (n = 3-5) animals were killed after 5, 10, 15, and 20 weeks of dosing and the distal end of the sciatic nerve was removed. The nerve was postfixed by immersion in neutral phosphate-buffered formalin, dehydrated in graded alcohols, and embedded in plastic embedding media. One-micrometer-thick sections were cut and stained with toluidine blue and basic fuchsin. Plasma levels of ddI on the day the animals were killed were greater than 10 microgram/ml within the first hour after dosing and fell rapidly to less than 1 microgram/ml (clinical range 1-2 microgram/ml) within 3 h after dosing. The abnormalities observed in the sciatic nerve were few, if any, after 5 or 10 weeks, but very prominent after 15 weeks of dosing. Four of the six ddI-treated rats exhibited abnormal morphology as evidenced by myelin splitting and ballooned myelin sheaths. Although abnormal morphology was present at 20 weeks of dosing, the effect was not as robust as at 15 weeks. This suggests that the nerve may partially recover from the effects of ddI with time. Published by Elsevier Science Inc.

Molecular cloning and high-level expression of human polymerase beta cDNA and comparison of the purified recombinant human and rat enzymes.

The cDNA encoding the human polymerase beta from HeLa cells was PCR amplified and cloned, and its nucleotide sequence determined. The DNA sequence is identical to the polymerase beta cDNA sequence from Tera-2 cells. Three expression strategies were employed that were designed to maximize translation initiation of the polymerase beta mRNA in Escherichia coli and all yielded a high level of human polymerase beta. The recombinant protein was purified and its properties were compared with those of the recombinant rat enzyme. The domain structure and kinetic parameters (k(cat) and K(m)) were nearly identical. A mouse IgG monoclonal antibody to the rat enzyme (mAb-10S) was approximately 10-fold less reactive with the human enzyme than with the rat enzyme as determined by ELISA.

Characterization of wild lambdoid bacteriophages: detection of a wide distribution of phage immunity groups and identification of a nus-dependent, nonlambdoid phage group.

Temperate phages were isolated from fresh human fecal samples. Lambdoid phages were screened for growth on Nus+ but not Nus- bacteria. Approximately 100 independent lysogens of Nus-dependent phages were constructed and tested for immunity to superinfection by the same Nus-dependent phages. This identified 20 different phage immunity groups, 18 of which belonged to the lambdoid phage family. The DNA from the majority of these phages hybridized with a lambda DNA probe, and approximately 50% were recognized by anti-lambda antibodies. Furthermore most were inducible by UV light. Eleven phage recombinants with different immunity were obtained when a phage from each group was coinfected with lambda or its derivative lambdaBLK20. We also identified another immunity group with 48 members. None of these hybridized with either lambda or phi80 DNA probes nor were they recognized by anti-lambda serum. Most were not induced by UV light treatment, and no recombinants were obtained when crossed with either lambda or lambdaBLK20. Consequently, this group of Nus-dependent phages represent a new nonlambdoid phage family.

Neurotransmitter transporters: target for endocrine regulation.

Aminergic signaling in the CNS is terminated by clearance from the synapse via high-affinity transporter molecules in the presynaptic membrane. Relatively recent sequence identification of these molecules has now permitted the initiation of studies of regulation of transporter function at the cellular and systems levels. In vitro studies provide evidence that the transporters for dopamine, serotonin, and gamma-aminobutyric acid are substrates for regulation by protein kinase C signaling. In vivo studies provide evidence that insulin and adrenal and gonadal steroid hormones may regulate the synthesis and activity of the transporters. Future directions should permit evaluation of the role of endocrine regulation in neurotransmitter clearance, and thus in the maintenance of normal CNS aminergic signaling.

Kainic acid (KA)-induced seizures in Sprague-Dawley rats and the effect of dietary taurine (TAU) supplementation or deficiency.

Male Sprague-Dawley rats received TAU supplementation (1.5% in drinking water) or TAU deficient diets for 4 weeks to test for a possible neuroprotective role of TAU in KA-induced (10 mg/kg s.c.) seizures. TAU supplementation significantly increased serum and hippocampal TAU levels, but not TAU content in temporal cortex or striatum. TAU deficient diets did not attenuate serum or tissue TAU levels. Dietary TAU supplementation failed to decrease the number or latency of partial or clonic-tonic seizures or wet dog shakes, whereas a TAU deficient diet decreased the number of clonictonic and partial seizures. This study does not support previous observations of an anticonvulsant effect of TAU against KA-induced seizures. KA-treatment decreased alpha 2-adrenergic receptor binding sites and TAU content in the temporal cortex across all dietary treatment groups, supporting previous evidence of severe KA-induced damage and neuronal loss in this brain region.

Sodium depletion and aldosterone decrease dopamine transporter activity in nucleus accumbens but not striatum.

Motivated behaviors, including sodium (Na) appetite, are correlated with increased dopamine (DA) transmission in the nucleus accumbens (NAc). DA transporter (DAT) modulation affects DA transmission and may play a role in motivated behaviors. In vivo Na depletion, which reliably induces Na appetite, was correlated with robust decreases in DA uptake via the DAT in the rat NAc with rotating disk electrode voltammetry [1,277 +/- 162 vs. 575 +/- 89 pmol. s-1. g-1; Vmax of transport for control vs. Na-depleted tissue]. Plasma aldosterone (Aldo) levels increase after in vivo Na depletion and contribute to Na appetite. Decreased DAT activity in the NAc was observed after in vitro Aldo treatment (428 +/- 28 vs. 300 +/- 25 pmol. s-1. g-1). Neither treatment affected DAT activity in the striatum. These results suggest that a direct action of Aldo is one possible mechanism by which Na depletion induces a reduction in DAT activity in the NAc. Reduced DAT activity may play a role in generating increased NAc DA transmission during Na appetite, which may underlie the motivating properties of Na for the Na-depleted rat.