It was generally accepted that dopamine receptors D1 (D1R)- and D2 (D2R)-expressing neurons are homogeneously and randomly distributed throughout the striatum. However, in reporter transgenic mice, the specific subregions of the caudal lateral striatum have been reported: the D1R-poor zone, in which D2R-expressing neurons are predominant, and the D2R-poor zone, in which D1R-expressing neurons are predominant. The present study demonstrated the presence of these distinct subregions not only in rodents but also in marmosets using endogenous dopamine receptors. We also showed that direct pathway medium spiny neurons in these distinct subregions preferentially project to parvalbumin-positive GABAergic neurons in the dorsal part of the substantia nigra pars lateralis. / 博士(理学) / Doctor of Philosophy in Science / 同志社大学 / Doshisha University

The purpose of this study was to investigate the ultrastructure of the membrana limitans interna (internal limiting membrane, ILM) and to evaluate alterations to the retinal cell layers after membrane peeling with vital dyes. Twenty-five patients (25 eyes) who underwent macular hole surgery were included, whereby 12 indocyanine green (ICG)- and 13 brilliant blue G (BBG)-stained ILM were analyzed using light, transmission electron and scanning electron microscopy. Retinal cell fragments on the ILM were identified in both groups using immunohistochemistry. Comparing ICG- and BBG-stained membranes, larger cellular fragments were observed at a higher frequency in the BBG group. Thereby, the findings indicate that ICG permits an enhanced separation of the ILM from the underlying retina with less mechanical destruction. A possible explanation might be seen in the known photosensitivity of ICG, which induces a stiffening and shrinkage of the ILM but also generates retinal toxic metabolites

No description available.

Parkinson’s disease is an age-related neurodegenerative disorder. The major symptoms of Parkinson’s disease are closely linked to the pathology of the disease. The main pathology of Parkinson’s disease consists of the degeneration of neurons of the substantia nigra pars compacta (SNpc), which leads to reduced amounts of dopamine in the brain. One of the treatment strategies in Parkinson’s disease is to conserve dopamine by inhibiting the enzymes responsible for its catabolism. The monoamine oxidase (MAO) B isoform catalyses the oxidation of dopamine in the central nervous system and is therefore an important target for Parkinson’s disease treatment. Inhibition of MAO-B provides symptomatic relief for Parkinson’s disease patients by increasing endogenous dopamine levels as well as enhancing the levels of dopamine after administration of levodopa (L-dopa), the metabolic precursor of dopamine. Recent studies have shown that phthalide can be used as a scaffold for the design of reversible MAO inhibitors. Although phthalide is a weak MAO-B inhibitor, substitution on the C5 position of phthalide yields highly potent reversible MAO-B inhibitors. In the present study, sesamol and benzodioxane were used as scaffolds for the design of MAO inhibitors. The structures of sesamol and benzodioxane closely resemble that of phthalide, which suggests that these moieties may be useful for the design of MAO inhibitors. This study may be viewed as an exploratory study to discover new scaffolds for MAO inhibition. Since substitution at C5 of phthalide with a benzyloxy side chain yielded particularly potent MAO inhibitors, the sesamol and benzodioxane derivatives possessed the benzyloxy substituent in the analogous positions to C5 of phthalide. These were the C5 and C6 positions of sesamol and benzodioxane, respectively. The sesamol and benzodioxane derivatives were synthesised by reacting sesamol and 6- hydroxy-1,4-benzodioxane, respectively, with an appropriate alkyl bromide in the presence of potassium carbonate (K2CO3) in N,N-dimethylformamide (DMF). 6-Hydroxy-1,4- benzodioxane, in turn, was synthesised from 1,4-benzodioxan-6-carboxaldehyde. The structures of the compounds were verified with nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses, while the purities were estimated by high-pressure liquid chromatography (HPLC). Sixteen sesamol and benzodioxane derivatives were synthesised. To determine the inhibition potencies of the synthesised compounds the recombinant human MAO-A and MAO-B enzymes were used. The inhibition potencies were expressed as the corresponding IC50 values. The results showed that the sesamol and benzodioxane derivatives are highly potent and selective inhibitors of MAO-B and to a lesser extent MAOA. The most potent MAO-B inhibitor was 6-(3-bromobenzyloxy)-1,4-benzodioxane with an IC50 value of 0.045 μM. All compounds examined displayed selectivity for the MAO-B isoform over MAO-A. Generally the benzodioxane derivatives were found to be more potent inhibitors of human MAO-A and MAO-B than the sesamol derivatives. The reversibility and mode of MAO-B inhibition of a representative derivative, 6-(3- bromobenzyloxy)-1,4-benzodioxane, was examined by measuring the degree to which the enzyme activity recovers after dialysis of enzyme-inhibitor complexes, while Lineweaver- Burk plots were constructed to determine whether the mode of inhibition is competitive. Since MAO-B activity is completely recovered after dialysis of enzyme-inhibitor mixtures, it was concluded that 6-(3-bromobenzyloxy)-1,4-benzodioxane binds reversibly to the MAO-B enzyme. The Lineweaver-Burk plots constructed were linear and intersected on the y-axis. Therefore it may be concluded that 6-(3-bromobenzyloxy)-1,4-benzodioxane is a competitive MAO-B inhibitor. To conclude, the C6-substituted benzodioxane derivatives are potent, selective, reversible and competitive inhibitors of human MAO-B. These compounds are therefore promising leads for the future development of therapy for Parkinson’s disease. / MSc (Pharmaceutical Chemistry), North-West University, Potchefstroom Campus, 2015

Parkinson’s disease is an age-related neurodegenerative disorder. The major symptoms of Parkinson’s disease are closely linked to the pathology of the disease. The main pathology of Parkinson’s disease consists of the degeneration of neurons of the substantia nigra pars compacta (SNpc), which leads to reduced amounts of dopamine in the brain. One of the treatment strategies in Parkinson’s disease is to conserve dopamine by inhibiting the enzymes responsible for its catabolism. The monoamine oxidase (MAO) B isoform catalyses the oxidation of dopamine in the central nervous system and is therefore an important target for Parkinson’s disease treatment. Inhibition of MAO-B provides symptomatic relief for Parkinson’s disease patients by increasing endogenous dopamine levels as well as enhancing the levels of dopamine after administration of levodopa (L-dopa), the metabolic precursor of dopamine. Recent studies have shown that phthalide can be used as a scaffold for the design of reversible MAO inhibitors. Although phthalide is a weak MAO-B inhibitor, substitution on the C5 position of phthalide yields highly potent reversible MAO-B inhibitors. In the present study, sesamol and benzodioxane were used as scaffolds for the design of MAO inhibitors. The structures of sesamol and benzodioxane closely resemble that of phthalide, which suggests that these moieties may be useful for the design of MAO inhibitors. This study may be viewed as an exploratory study to discover new scaffolds for MAO inhibition. Since substitution at C5 of phthalide with a benzyloxy side chain yielded particularly potent MAO inhibitors, the sesamol and benzodioxane derivatives possessed the benzyloxy substituent in the analogous positions to C5 of phthalide. These were the C5 and C6 positions of sesamol and benzodioxane, respectively. The sesamol and benzodioxane derivatives were synthesised by reacting sesamol and 6- hydroxy-1,4-benzodioxane, respectively, with an appropriate alkyl bromide in the presence of potassium carbonate (K2CO3) in N,N-dimethylformamide (DMF). 6-Hydroxy-1,4- benzodioxane, in turn, was synthesised from 1,4-benzodioxan-6-carboxaldehyde. The structures of the compounds were verified with nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses, while the purities were estimated by high-pressure liquid chromatography (HPLC). Sixteen sesamol and benzodioxane derivatives were synthesised. To determine the inhibition potencies of the synthesised compounds the recombinant human MAO-A and MAO-B enzymes were used. The inhibition potencies were expressed as the corresponding IC50 values. The results showed that the sesamol and benzodioxane derivatives are highly potent and selective inhibitors of MAO-B and to a lesser extent MAOA. The most potent MAO-B inhibitor was 6-(3-bromobenzyloxy)-1,4-benzodioxane with an IC50 value of 0.045 μM. All compounds examined displayed selectivity for the MAO-B isoform over MAO-A. Generally the benzodioxane derivatives were found to be more potent inhibitors of human MAO-A and MAO-B than the sesamol derivatives. The reversibility and mode of MAO-B inhibition of a representative derivative, 6-(3- bromobenzyloxy)-1,4-benzodioxane, was examined by measuring the degree to which the enzyme activity recovers after dialysis of enzyme-inhibitor complexes, while Lineweaver- Burk plots were constructed to determine whether the mode of inhibition is competitive. Since MAO-B activity is completely recovered after dialysis of enzyme-inhibitor mixtures, it was concluded that 6-(3-bromobenzyloxy)-1,4-benzodioxane binds reversibly to the MAO-B enzyme. The Lineweaver-Burk plots constructed were linear and intersected on the y-axis. Therefore it may be concluded that 6-(3-bromobenzyloxy)-1,4-benzodioxane is a competitive MAO-B inhibitor. To conclude, the C6-substituted benzodioxane derivatives are potent, selective, reversible and competitive inhibitors of human MAO-B. These compounds are therefore promising leads for the future development of therapy for Parkinson’s disease. / MSc (Pharmaceutical Chemistry), North-West University, Potchefstroom Campus, 2015

The transmission of sex pheromone-mediated signals is essential for goldfish reproduction. However, the neural pathways underlying this reproductive signalling pathway in the goldfish brain is not well described. Lesioning experiments have shown previously that two brain areas, the preoptic area (POA) and the ventral telencephali pars ventralis (Vv) in particular, are important for reproduction. We used patch clamp electrophysiology to study the electrical activities of POA and Vv neurons. Based on the intrinsic properties of these neurons, we suggest there are five different functional classes of POA neurons and a single class of Vv neurons. In addition, by electrically stimulating the olfactory bulb (OB), we were able to show that this primary sensory structure makes monosynaptic glutamatergic connections with both POA and Vv neurons. While electrophysiology measures signalling events occurring at short time scales on the order of milliseconds to minutes, we were also interested in studying sex pheromone signalling in the goldfish brain over a long time scale. Thus, we describe changes in gene expression in male goldfish exposed to waterborne sex pheromones (17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha) over 6 hours. We perform cDNA microarrays on Prostaglandin-F2alpha-treated fish to study the rapid modulation of transcription and define the signalling pathways affected. Our microarrays showed that 71 genes were differentially regulated (67 up and 4 down). Through gene ontology enrichment analysis, we found that these genes were involved in various biological processes such as RNA processing, neurotransmission, neuronal development, apoptosis, cellular metabolism and sexual reproduction. RT-PCRs were performed to validate our microarrays and to facilitate direct comparisons of the effects of the two sex pheromones, 17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha. By combining electrophysiology and gene expression analyses, we were able to study sex-pheromone signalling on two different time scales. One short, occurring on the order of milliseconds to minutes, that involves electrical activities in the brain through the glutamatergic amino-3-hydroxy-5-methylisoxazole-4-propionate and N-methyl-D-aspartate receptors; and the other long occurring several hours later that involves changes in the gene expression levels of calmodulin and ependymin among other genes underlying neuroplasticity. Reproductive neuroplasticity in the goldfish may therefore require the activation of glutamatergic receptors which then activate downstream signals like calmodulin and ependymin to transform the sex pheromones-mediate signal into gene expression.

<p><strong>Sammanfattning</strong></p><p>Syfte: Syftet med denna studie var att undersöka samband mellan några utvalda faktorer av betydelse vid förskrivning av fysisk aktivitet på recept (FaR) på hälso- och vårdcentraler i Sverige.</p><p>Metod: En enkätundersökning genomfördes på 37 icke-privata hälso- och vårdcentraler i Malmö, Stockholm och Umeå. Totalt 241 enkäter besvarades av legitimerad personal med förskrivningsrätt av FaR. Studerade faktorer, uttryckta som enkätfrågor, var: förskrivarens<em> kön, ålder, befattning, landstingstillhörighet, användning av FaR/FYSS, egen motion, FaR-utbildning, tidsbrist, riktlinjer, uppföljning, samarbete med friskvårdsaktör, FaR-ansvarig, hänvisning av FaR-patienter, kunskap i att motivera till fysisk aktivitet </em>samt<em> kunskap om vilka sjukdomstillstånd som kan behandlas med fysisk aktivitet</em>. En webb-baserad enkät distri-buerades och samlades in via e-post och en pappersenkät användes på ett par hälso- och vårdcentraler. Resultatet från enkätundersökningen analyserades med chitvåtest och binär logistisk regression. </p><p>Resultat: Sannolikheten att förskriva FaR var signifikant sju gånger högre hos personal som visste vart de kunde <em>hänvisa patienter med FaR-ordination</em> i jämförelse med dem som inte visste vart hänvisning kunde ske. Vidare var sannolikheten att förskriva FaR signifikant fyra gånger högre hos personal med specifik <em>utbildning om FaR</em> i jämförelse med dem som inte hade någon FaR-utbildning. I undersökningen framkom även att förskrivning av FaR samvarierade signifikant med faktorerna <em>befattning, landstingstillhörighet, samarbete med friskvårdsaktör/-er, riktlinjer från arbetsgivaren, kunskap om vilka sjukdomstillstånd som kan behandlas med fysisk aktivitet</em> samt <em>kunskap i att motivera patienter till fysisk aktivitet</em>. Ingen signifikant samvariation sågs mellan förskrivning av FaR och följande faktorer: förskrivarens <em>kön</em>, <em>ålder</em>, <em>användning av FaR/FYSS</em>, <em>egen motion</em>, <em>FaR-ansvarig</em>, <em>uppföljning</em> samt <em>om personalen avstår från att förskriva FaR pga att det förlänger patientbesöken</em>.</p><p>Slutsats: Vid arbete med FaR är det viktigt att skapa tydliga <em>riktlinjer</em>, <em>samarbeta med frisk-vårdsaktör/-er</em>, <em>att personalen har kunskap om vilka sjukdomstillstånd som kan behandlas med fysisk aktivitet</em> samt om<em> motivation till fysisk aktivitet</em>. Vi vill poängtera att det framförallt är viktigt att personalen är <em>utbildad om FaR</em> samt att de vet vart de kan <em>hänvisa patienter med FaR-ordination</em> i syfte att effektivisera FaR som arbetsmetod på hälso- och vårdcentraler i Sverige.</p> / <p><strong>Abstract</strong></p><p>Aim: The aim of this study was to examine relations between selected factors significant to the prescription of Physical Activity Referral Scheme (PAR, Swedish: Fysisk aktivitet på recept, FaR) at health centers in Sweden.</p><p>Method: A questionnaire study was carried out within 37 non-private health centers in Malmö, Stockholm and Umeå. A total of 241 questionnaires were answered by personnel authorized to prescribe FaR. Studied factors, expressed as questions in the questionnaire, were: prescriptors<em> sex, age, profession, county council, the use of FaR/FYSS, personal exer-cise, FaR-education, lack of time, guidelines, follow-up, cooperation with preventive health care centers, FaR-coordinator, reference of FaR-patients, knowledge about how to inspire people to physical activity </em>and<em> knowledge about which conditions/diseases that can be treated with physical activity</em>. A web-based questionnaire was distributed and collected through e-mail and a questionnaire in paperform was used at a couple of health centers. Results from the questionnaire were analysed with chi-square test and binary logistic regression.</p><p>Results:  The probability to prescribe FaR was significantly seven times higher for personnel who knew where to <em>refer FaR-patients</em> compared to those who did not know where reference could be given. Further the probability to prescribe FaR was significantly four times higher for personnel with specific<em> FaR-education</em> compared to those who lacked FaR-education. The study also showed that FaR-prescription had significant covariation with the factors <em>profession, county council, cooperation with preventive health care centers, guidelines from the employer, knowledge about what conditions/diseases that can be treated with physical activity</em> and <em>knowledge about how to motivate patients to physical activity</em>. No significant covariation were found between FaR-prescription and the following factors: prescriptors <em>sex</em>, <em>age</em>, <em>use of FaR/FYSS</em>, <em>personal exercise</em>, <em>FaR-coordinator</em>, <em>follow-up</em> or <em>if personnel refrain from prescribing FaR because it extends patient visiting-hours.</em></p><p>Conclusion: When working with FaR it is important to create clear <em>guidelines</em>, <em>cooperate with preventive health care centers</em>, that the personnel has<em> knowledge about conditions/diseases which can be treated with physical activity</em> and <em>motivation to physical activity.</em> Above all we want to point out that it is important that the personnel is educated about FaR and that they know where to refer patients with FaR-prescription in order to make the working method more effective at health centers in Sweden.</p>

Sammanfattning Syfte: Syftet med denna studie var att undersöka samband mellan några utvalda faktorer av betydelse vid förskrivning av fysisk aktivitet på recept (FaR) på hälso- och vårdcentraler i Sverige. Metod: En enkätundersökning genomfördes på 37 icke-privata hälso- och vårdcentraler i Malmö, Stockholm och Umeå. Totalt 241 enkäter besvarades av legitimerad personal med förskrivningsrätt av FaR. Studerade faktorer, uttryckta som enkätfrågor, var: förskrivarens kön, ålder, befattning, landstingstillhörighet, användning av FaR/FYSS, egen motion, FaR-utbildning, tidsbrist, riktlinjer, uppföljning, samarbete med friskvårdsaktör, FaR-ansvarig, hänvisning av FaR-patienter, kunskap i att motivera till fysisk aktivitet samt kunskap om vilka sjukdomstillstånd som kan behandlas med fysisk aktivitet. En webb-baserad enkät distri-buerades och samlades in via e-post och en pappersenkät användes på ett par hälso- och vårdcentraler. Resultatet från enkätundersökningen analyserades med chitvåtest och binär logistisk regression.  Resultat: Sannolikheten att förskriva FaR var signifikant sju gånger högre hos personal som visste vart de kunde hänvisa patienter med FaR-ordination i jämförelse med dem som inte visste vart hänvisning kunde ske. Vidare var sannolikheten att förskriva FaR signifikant fyra gånger högre hos personal med specifik utbildning om FaR i jämförelse med dem som inte hade någon FaR-utbildning. I undersökningen framkom även att förskrivning av FaR samvarierade signifikant med faktorerna befattning, landstingstillhörighet, samarbete med friskvårdsaktör/-er, riktlinjer från arbetsgivaren, kunskap om vilka sjukdomstillstånd som kan behandlas med fysisk aktivitet samt kunskap i att motivera patienter till fysisk aktivitet. Ingen signifikant samvariation sågs mellan förskrivning av FaR och följande faktorer: förskrivarens kön, ålder, användning av FaR/FYSS, egen motion, FaR-ansvarig, uppföljning samt om personalen avstår från att förskriva FaR pga att det förlänger patientbesöken. Slutsats: Vid arbete med FaR är det viktigt att skapa tydliga riktlinjer, samarbeta med frisk-vårdsaktör/-er, att personalen har kunskap om vilka sjukdomstillstånd som kan behandlas med fysisk aktivitet samt om motivation till fysisk aktivitet. Vi vill poängtera att det framförallt är viktigt att personalen är utbildad om FaR samt att de vet vart de kan hänvisa patienter med FaR-ordination i syfte att effektivisera FaR som arbetsmetod på hälso- och vårdcentraler i Sverige. / Abstract Aim: The aim of this study was to examine relations between selected factors significant to the prescription of Physical Activity Referral Scheme (PAR, Swedish: Fysisk aktivitet på recept, FaR) at health centers in Sweden. Method: A questionnaire study was carried out within 37 non-private health centers in Malmö, Stockholm and Umeå. A total of 241 questionnaires were answered by personnel authorized to prescribe FaR. Studied factors, expressed as questions in the questionnaire, were: prescriptors sex, age, profession, county council, the use of FaR/FYSS, personal exer-cise, FaR-education, lack of time, guidelines, follow-up, cooperation with preventive health care centers, FaR-coordinator, reference of FaR-patients, knowledge about how to inspire people to physical activity and knowledge about which conditions/diseases that can be treated with physical activity. A web-based questionnaire was distributed and collected through e-mail and a questionnaire in paperform was used at a couple of health centers. Results from the questionnaire were analysed with chi-square test and binary logistic regression. Results:  The probability to prescribe FaR was significantly seven times higher for personnel who knew where to refer FaR-patients compared to those who did not know where reference could be given. Further the probability to prescribe FaR was significantly four times higher for personnel with specific FaR-education compared to those who lacked FaR-education. The study also showed that FaR-prescription had significant covariation with the factors profession, county council, cooperation with preventive health care centers, guidelines from the employer, knowledge about what conditions/diseases that can be treated with physical activity and knowledge about how to motivate patients to physical activity. No significant covariation were found between FaR-prescription and the following factors: prescriptors sex, age, use of FaR/FYSS, personal exercise, FaR-coordinator, follow-up or if personnel refrain from prescribing FaR because it extends patient visiting-hours. Conclusion: When working with FaR it is important to create clear guidelines, cooperate with preventive health care centers, that the personnel has knowledge about conditions/diseases which can be treated with physical activity and motivation to physical activity. Above all we want to point out that it is important that the personnel is educated about FaR and that they know where to refer patients with FaR-prescription in order to make the working method more effective at health centers in Sweden.

The transmission of sex pheromone-mediated signals is essential for goldfish reproduction. However, the neural pathways underlying this reproductive signalling pathway in the goldfish brain is not well described. Lesioning experiments have shown previously that two brain areas, the preoptic area (POA) and the ventral telencephali pars ventralis (Vv) in particular, are important for reproduction. We used patch clamp electrophysiology to study the electrical activities of POA and Vv neurons. Based on the intrinsic properties of these neurons, we suggest there are five different functional classes of POA neurons and a single class of Vv neurons. In addition, by electrically stimulating the olfactory bulb (OB), we were able to show that this primary sensory structure makes monosynaptic glutamatergic connections with both POA and Vv neurons. While electrophysiology measures signalling events occurring at short time scales on the order of milliseconds to minutes, we were also interested in studying sex pheromone signalling in the goldfish brain over a long time scale. Thus, we describe changes in gene expression in male goldfish exposed to waterborne sex pheromones (17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha) over 6 hours. We perform cDNA microarrays on Prostaglandin-F2alpha-treated fish to study the rapid modulation of transcription and define the signalling pathways affected. Our microarrays showed that 71 genes were differentially regulated (67 up and 4 down). Through gene ontology enrichment analysis, we found that these genes were involved in various biological processes such as RNA processing, neurotransmission, neuronal development, apoptosis, cellular metabolism and sexual reproduction. RT-PCRs were performed to validate our microarrays and to facilitate direct comparisons of the effects of the two sex pheromones, 17alpha,20beta dihydroxy-4-pregene-3-one and Prostaglandin-F2alpha. By combining electrophysiology and gene expression analyses, we were able to study sex-pheromone signalling on two different time scales. One short, occurring on the order of milliseconds to minutes, that involves electrical activities in the brain through the glutamatergic amino-3-hydroxy-5-methylisoxazole-4-propionate and N-methyl-D-aspartate receptors; and the other long occurring several hours later that involves changes in the gene expression levels of calmodulin and ependymin among other genes underlying neuroplasticity. Reproductive neuroplasticity in the goldfish may therefore require the activation of glutamatergic receptors which then activate downstream signals like calmodulin and ependymin to transform the sex pheromones-mediate signal into gene expression.

Dopamine (DA) neurons of the substantia nigra pars compacta (SNc) have a key role in regulation of voluntary movement control. Their death is a hallmark of Parkinson’s disease, characterised by inhibited motor control, including muscle rigidity and tremor. Excitatory input to SNc-DA neurons is primarily from the subthalamic nucleus, and in PD these afferents display a higher frequency firing, as well as increased burst firing, which could cause increased excitatory activity in SNc-DA neurons. NMDA receptors (NMDARs) bind the excitatory neurotransmitter glutamate, and are essential for learning and memory. In SNc-DA neurons, NMDARs have a putative triheteromeric subunit arrangement of GluN1 plus GluN2B and/or GluN2D. Wild type (WT) mice, and those lacking the gene for GluN2D (Grin2D-null), were used to explore its role in various aspects of DA neuronal function and dysfunction using patch-clamp electrophysiology, viability assaying, and immunofluorescence. Pharmacological intervention using subunit-specific inhibitors ifenprodil and DQP-1105 on elicited NMDAR-EPSCs suggested a developmental shift from primarily GluN2B to GluN2B/D. Activity dependent regulation was assessed by high frequency burst stimulation of glutamatergic afferents: in comparison to controls, significant downregulation of NMDARs was observed in SNc-DA neurons, though no differences were observed based on genotype. This regulatory function may be a neuroprotective or homeostatic response. Ambient extracellular glutamate elicits tonic NMDAR activity in SNc-DA neurons, which may be important for maintaining basal levels of excitability: the role of GluN2D was assessed by recording the deflection in baseline current caused by application of competitive NMDAR antagonist D-AP5. There was a significantly larger NMDAR-mediated current in WT vs Grin2D-null mice, indicating that GluN2D has a role in binding ambient glutamate. Dysfunction of glutamate uptake could be a secondary pathophysiological occurrence in the SNc, leading to increased ambient glutamate: the effect of this was explored by application of the competitive glutamate transporter blocker TBOA. Here, the NMDAR-mediated portion of this current was significantly higher in WT mice in comparison to Grin2D-null. Interestingly, dose-response data obtained from bath application of NMDA showed significantly larger currents in Grin2D-null animals vs WT, but only at the top of the response curve (~1-10 mM), which may indicate a capability for larger conductance in Grin2D-null animals at high NMDAR saturation due to replacement of GluN2D with GluN2B. GluN2D may therefore be neuroprotective, by attenuating peak current flow in response to very high agonist concentrations. Lastly, GluN2D has been found to decrease NMDAR open probability under hypoxic conditions, potentially conferring resistance to hypoxia / ischemia related excitotoxicity. Therefore, low (15% O2 / 80% N2 / 5% CO2) vs high (95% O2 / 5% CO2) oxygen conditions were used along with immunofluorescent propidium iodide cell death assaying and immunofluorescent labeling for DA neurons in order to compare levels of DA neuronal death in the SNc based on oxygen status and genotype. Whilst there was a significant submaximal effect based on O2 status, genotype did not confer a practical resistance under these conditions. In summary, NMDARs have diverse roles in SNc-DA neurons which may both serve to maintain normal function and protect the cell against potentially pathological conditions.