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  1. Article ; Online: Dopamine Transporter Localization in Medial Forebrain Bundle Axons Indicates Its Long-Range Transport Primarily by Membrane Diffusion with a Limited Contribution of Vesicular Traffic on Retromer-Positive Compartments.

    Bagalkot, Tarique R / Block, Ethan R / Bucchin, Kristen / Balcita-Pedicino, Judith Joyce / Calderon, Michael / Sesack, Susan R / Sorkin, Alexander

    The Journal of neuroscience : the official journal of the Society for Neuroscience

    2020  Volume 41, Issue 2, Page(s) 234–250

    Abstract: Dopamine transporter (DAT) controls dopamine neurotransmission by clearing synaptically released dopamine. However, trafficking itineraries of DAT, which determine its cell-surface concentration near synapses, are poorly characterized. It is especially ... ...

    Abstract Dopamine transporter (DAT) controls dopamine neurotransmission by clearing synaptically released dopamine. However, trafficking itineraries of DAT, which determine its cell-surface concentration near synapses, are poorly characterized. It is especially unknown how DAT is transported between spatially distant midbrain somatodendritic and striatal axonal compartments. To examine this "long-range" trafficking, the localization and membrane diffusion of HA-epitope tagged DAT in the medial forebrain bundle (MFB) of a knock-in mouse (both sexes) were analyzed using confocal, super-resolution and EM in intact brain and acute brain slices. HA-DAT was abundant in the plasma membrane of MFB axons, similar to the striatum, although the intracellular fraction of HA-DAT in MFB was more substantial. Intracellular HA-DAT colocalized with VPS35, a subunit of the retromer complex mediating recycling from endosomes, in a subset of axons. Late endosomes, lysosomes, and endoplasmic reticulum were abundant in the soma but minimally present in MFB axons, suggesting that biosynthesis and lysosomal degradation of DAT are confined to soma. Together, the data suggest that membrane diffusion is the main mode of long-range DAT transport through MFB, although the contribution of vesicular traffic can be significant in a population of MFB axons. Based on HA-DAT diffusion rates, plasma membrane DAT in MFB axons turns over with a halftime of ∼20 d, which explains the extremely slow turnover of DAT protein in the brain. Unexpectedly, the mean diameter of DAT-labeled MFB axons was observed to be twice larger than reported for striatum. The implications of this finding for dopamine neuron physiology are discussed.
    MeSH term(s) Animals ; Axons/metabolism ; Axons/ultrastructure ; Cell Membrane/metabolism ; Diffusion ; Dopamine Plasma Membrane Transport Proteins/genetics ; Dopamine Plasma Membrane Transport Proteins/metabolism ; Endosomes/metabolism ; Female ; Gene Knock-In Techniques ; Humans ; Kinetics ; Lysosomes/metabolism ; Male ; Medial Forebrain Bundle/metabolism ; Medial Forebrain Bundle/ultrastructure ; Mice ; Mice, Inbred C57BL ; Synaptic Vesicles/metabolism ; Vesicular Monoamine Transport Proteins/metabolism
    Chemical Substances Dopamine Plasma Membrane Transport Proteins ; Slc18a2 protein, mouse ; Vesicular Monoamine Transport Proteins
    Language English
    Publishing date 2020-11-24
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 604637-x
    ISSN 1529-2401 ; 0270-6474
    ISSN (online) 1529-2401
    ISSN 0270-6474
    DOI 10.1523/JNEUROSCI.0744-20.2020
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Subcellular localization of D2 receptors in the murine substantia nigra.

    Lebowitz, Joseph J / Trinkle, Mason / Bunzow, James R / Balcita-Pedicino, Judith Joyce / Hetelekides, Savas / Robinson, Brooks / De La Torre, Santiago / Aicher, Sue A / Sesack, Susan R / Williams, John T

    Brain structure & function

    2021  Volume 227, Issue 3, Page(s) 925–941

    Abstract: G-protein-coupled D2 autoreceptors expressed on dopamine neurons (D2Rs) inhibit transmitter release and cell firing at axonal endings and somatodendritic compartments. Mechanistic details of somatodendritic dopamine release remain unresolved, partly due ... ...

    Abstract G-protein-coupled D2 autoreceptors expressed on dopamine neurons (D2Rs) inhibit transmitter release and cell firing at axonal endings and somatodendritic compartments. Mechanistic details of somatodendritic dopamine release remain unresolved, partly due to insufficient information on the subcellular distribution of D2Rs. Previous studies localizing D2Rs have been hindered by a dearth of antibodies validated for specificity in D2R knockout animals and have been limited by the small sampling areas imaged by electron microscopy. This study utilized sub-diffraction fluorescence microscopy and electron microscopy to examine D2 receptors in a superecliptic pHlourin GFP (SEP) epitope-tagged D2 receptor knockin mouse. Incubating live slices with an anti-SEP antibody achieved the selective labeling of plasma membrane-associated receptors for immunofluorescent imaging over a large area of the substantia nigra pars compacta (SNc). SEP-D2Rs appeared as puncta-like structures along the surface of dendrites and soma of dopamine neurons visualized by antibodies to tyrosine hydroxylase (TH). TH-associated SEP-D2Rs displayed a cell surface density of 0.66 puncta/µm
    MeSH term(s) Animals ; Autoreceptors/metabolism ; Dopamine/metabolism ; Dopaminergic Neurons/metabolism ; Mice ; Receptors, Dopamine D2/analysis ; Receptors, Dopamine D2/metabolism ; Substantia Nigra/metabolism
    Chemical Substances Autoreceptors ; DRD2 protein, mouse ; Receptors, Dopamine D2 ; Dopamine (VTD58H1Z2X)
    Language English
    Publishing date 2021-12-02
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2273162-3
    ISSN 1863-2661 ; 1863-2653
    ISSN (online) 1863-2661
    ISSN 1863-2653
    DOI 10.1007/s00429-021-02432-3
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Impact of prenatal nicotine on the structure of midbrain dopamine regions in the rat.

    Omelchenko, Natalia / Roy, Priya / Balcita-Pedicino, Judith Joyce / Poloyac, Samuel / Sesack, Susan R

    Brain structure & function

    2016  Volume 221, Issue 4, Page(s) 1939–1953

    Abstract: In utero exposure of rats to nicotine (NIC) provides a useful animal model for studying the impact of smoking during pregnancy on human offspring. Certain sequelae of prenatal NIC exposure suggest an impact on the development of the midbrain dopamine (DA) ...

    Abstract In utero exposure of rats to nicotine (NIC) provides a useful animal model for studying the impact of smoking during pregnancy on human offspring. Certain sequelae of prenatal NIC exposure suggest an impact on the development of the midbrain dopamine (DA) system, which receives a robust cholinergic innervation from the mesopontine tegmentum. We therefore investigated whether prenatal NIC induced structural changes in cells and synapses within the midbrain that persisted into adulthood. Osmotic minipumps delivering either sodium bitartrate (vehicle; VEH) or NIC bitartrate at 2 mg/kg/day were implanted into nine timed-pregnant dams at E4. At birth, rat pups were culled to litters of six males each, and the litters were cross-fostered. Plasma levels of NIC and cotinine from killed pups provided evidence of NIC exposure in utero. Pups separated from dams at weaning showed a trend toward reduced locomotor activity at this time point but not when tested again in adulthood. Adult rats were killed for anatomical studies. Estimates of brain size and volume did not vary with NIC treatment. Midbrain sections stained for Nissl or by immunoperoxidase for tyrosine hydroxylase and analyzed using unbiased stereology revealed no changes in volume or cell number in the substantia nigra compacta or ventral tegmental area as a result of NIC exposure. Within the ventral tegmental area, electron microscopic physical disector analysis showed no significant differences in the number of axon terminals or the number of asymmetric (putative excitatory) or symmetric (putative inhibitory) synapses. Although too infrequent to estimate by unbiased stereology, no obvious difference in the proportion of cholinergic axons was noted in NIC- versus VEH-treated animals. These data suggest that activation of nicotinic receptors during prenatal development induces no significant modifications in the structure of cells in the ventral midbrain when assessed in adulthood.
    MeSH term(s) Animals ; Axons/drug effects ; Axons/pathology ; Axons/ultrastructure ; Brain/drug effects ; Brain/pathology ; Brain/ultrastructure ; Cotinine/blood ; Dopamine/metabolism ; Dopaminergic Neurons/drug effects ; Dopaminergic Neurons/pathology ; Dopaminergic Neurons/ultrastructure ; Female ; Locomotion/drug effects ; Male ; Mesencephalon/drug effects ; Mesencephalon/pathology ; Mesencephalon/ultrastructure ; Nicotine/administration & dosage ; Nicotine/blood ; Pars Compacta/drug effects ; Pars Compacta/pathology ; Pars Compacta/ultrastructure ; Pregnancy ; Prenatal Exposure Delayed Effects/pathology ; Rats ; Synapses/drug effects ; Synapses/pathology ; Synapses/ultrastructure ; Tyrosine 3-Monooxygenase/metabolism ; Ventral Tegmental Area/drug effects ; Ventral Tegmental Area/pathology ; Ventral Tegmental Area/ultrastructure
    Chemical Substances Nicotine (6M3C89ZY6R) ; Tyrosine 3-Monooxygenase (EC 1.14.16.2) ; Cotinine (K5161X06LL) ; Dopamine (VTD58H1Z2X)
    Language English
    Publishing date 2016-05
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2273162-3
    ISSN 1863-2661 ; 1863-2653
    ISSN (online) 1863-2661
    ISSN 1863-2653
    DOI 10.1007/s00429-015-1014-y
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: The inhibitory influence of the lateral habenula on midbrain dopamine cells: ultrastructural evidence for indirect mediation via the rostromedial mesopontine tegmental nucleus.

    Balcita-Pedicino, Judith Joyce / Omelchenko, Natalia / Bell, Roland / Sesack, Susan R

    The Journal of comparative neurology

    2011  Volume 519, Issue 6, Page(s) 1143–1164

    Abstract: The lateral habenula (LHb) provides an important source of negative reinforcement signals to midbrain dopamine (DA) cells in the substantia nigra and ventral tegmental area (VTA). This profound and consistent inhibitory influence involves a disynaptic ... ...

    Abstract The lateral habenula (LHb) provides an important source of negative reinforcement signals to midbrain dopamine (DA) cells in the substantia nigra and ventral tegmental area (VTA). This profound and consistent inhibitory influence involves a disynaptic connection from glutamate neurons in the LHb to some population of γ-aminobutyric acid (GABA) cells that, in turn, innervates DA neurons. Previous studies demonstrated that the GABA cells intrinsic to the VTA receive insufficient synaptic input from the LHb to serve as the primary source of this intermediate connection. In this investigation, we sought ultrastructural evidence supporting the hypothesis that a newly identified region of the brainstem, the rostromedial mesopontine tegmental nucleus (RMTg), is a more likely candidate for inhibiting midbrain DA cells in response to LHb activation. Electron microscopic examination of rat brain sections containing dual immunoreactivity for an anterograde tracing agent and a phenotypic marker revealed that: 1) more than 55% of the synapses formed by LHb axons in the RMTg were onto GABA-labeled dendrites; 2) more than 80% of the synapses formed by RMTg axons in the VTA contacted dendrites immunoreactive for the DA synthetic enzyme tyrosine hydroxylase; and 3) nearly all RMTg axons formed symmetric synapses and contained postembedding immunoreactivity for GABA. These findings indicate that the newly identified RMTg region is an intermediate structure in a disynaptic pathway that connects the LHb to VTA DA neurons. The results have important implications for understanding mental disorders characterized by a dysregulation of reward circuitry involving LHb and DA cell populations.
    MeSH term(s) Animals ; Dopamine/metabolism ; Habenula/metabolism ; Habenula/ultrastructure ; Immunohistochemistry ; Male ; Mesencephalon/metabolism ; Mesencephalon/ultrastructure ; Neural Pathways/metabolism ; Neural Pathways/ultrastructure ; Neurons/metabolism ; Neurons/ultrastructure ; Rats ; Rats, Sprague-Dawley ; Tegmentum Mesencephali/metabolism ; Tegmentum Mesencephali/ultrastructure
    Chemical Substances Dopamine (VTD58H1Z2X)
    Language English
    Publishing date 2011-01-21
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 3086-7
    ISSN 1096-9861 ; 0021-9967 ; 0092-7317
    ISSN (online) 1096-9861
    ISSN 0021-9967 ; 0092-7317
    DOI 10.1002/cne.22561
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  5. Article: Orexin axons in the rat ventral tegmental area synapse infrequently onto dopamine and gamma-aminobutyric acid neurons.

    Balcita-Pedicino, Judith Joyce / Sesack, Susan R

    The Journal of comparative neurology

    2007  Volume 503, Issue 5, Page(s) 668–684

    Abstract: Cells in the ventral tegmental area (VTA) facilitate motivated behaviors, and the activity of VTA neurons is regulated by dense projections from the lateral hypothalamic area (LHA). Orexin (Orx) neurons in the lateral and perifornical hypothalamus play ... ...

    Abstract Cells in the ventral tegmental area (VTA) facilitate motivated behaviors, and the activity of VTA neurons is regulated by dense projections from the lateral hypothalamic area (LHA). Orexin (Orx) neurons in the lateral and perifornical hypothalamus play important roles in arousal, feeding, and energy metabolism. Orx cells contribute substantially to the LHA projection to the rat midbrain. However, the morphological features of Orx fibers in the VTA and whether they synapse onto dopamine (DA) or gamma-aminobutyric acid (GABA) neurons have not yet been investigated. We utilized immunoperoxidase and immunogold-silver staining to examine the morphological features and synaptic incidence of Orx-labeled axons in the VTA. We then combined immunoperoxidase labeling for Orx with immunogold-silver labeling for GABA or for tyrosine hydroxylase (TH) in DA neurons. Electron microscopic analysis revealed that most Orx-labeled axons in the VTA were passing fibers. The less common Orx varicosities were occasionally apposed to TH- or GABA-labeled dendrites without synapsing. Only a small proportion of Orx-positive axons synapsed onto dendrites or soma. The synapses included both asymmetric and symmetric types and targeted TH- and GABA-labeled profiles with equal frequency. These findings suggest that most Orx fibers in the VTA are axons passing to caudal brainstem structures. However, Orx does mediate some direct synaptic influence on VTA DA and GABA neurons. Additional nonsynaptic effects are suggested by the presence of numerous dense-cored vesicles. These studies have important implications for understanding the mechanisms whereby Orx can alter behavior through regulating VTA DA and GABA cell activity.
    MeSH term(s) Animals ; Axons/metabolism ; Axons/ultrastructure ; Dopamine/metabolism ; Intracellular Signaling Peptides and Proteins/metabolism ; Male ; Microscopy, Immunoelectron/methods ; Neurons/cytology ; Neurons/metabolism ; Neuropeptides/metabolism ; Orexins ; Rats ; Rats, Sprague-Dawley ; Silver Staining/methods ; Synapses/diagnostic imaging ; Synapses/metabolism ; Ultrasonography ; Ventral Tegmental Area/cytology ; gamma-Aminobutyric Acid/metabolism
    Chemical Substances Intracellular Signaling Peptides and Proteins ; Neuropeptides ; Orexins ; gamma-Aminobutyric Acid (56-12-2) ; Dopamine (VTD58H1Z2X)
    Language English
    Publishing date 2007-08-10
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 3086-7
    ISSN 1096-9861 ; 0021-9967 ; 0092-7317
    ISSN (online) 1096-9861
    ISSN 0021-9967 ; 0092-7317
    DOI 10.1002/cne.21420
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Brain Region-Specific Trafficking of the Dopamine Transporter.

    Block, Ethan R / Nuttle, Jacob / Balcita-Pedicino, Judith Joyce / Caltagarone, John / Watkins, Simon C / Sesack, Susan R / Sorkin, Alexander

    The Journal of neuroscience : the official journal of the Society for Neuroscience

    2015  Volume 35, Issue 37, Page(s) 12845–12858

    Abstract: The dopamine (DA) transporter (DAT) controls dopaminergic neurotransmission by removing extracellular DA. Although DA reuptake is proposed to be regulated by DAT traffic to and from the cell surface, the membrane trafficking system involved in the ... ...

    Abstract The dopamine (DA) transporter (DAT) controls dopaminergic neurotransmission by removing extracellular DA. Although DA reuptake is proposed to be regulated by DAT traffic to and from the cell surface, the membrane trafficking system involved in the endocytic cycling of DAT in the intact mammalian brain has not been characterized. Hence, we performed immunolabeling and quantitative analysis of the subcellular and regional distribution of DAT using the transgenic knock-in mouse expressing hemagglutinin (HA) epitope-tagged DAT (HA-DAT) and by using a combination of electron microscopy and a novel method for immunofluorescence labeling of HA-DAT in acute sagittal brain slices. Both approaches demonstrated that, in midbrain somatodendritic regions, HA-DAT was present in the plasma membrane, endoplasmic reticulum, and Golgi complex, with a small fraction in early and recycling endosomes and an even smaller fraction in late endosomes and lysosomes. In the striatum and in axonal tracts between the midbrain and striatum, HA-DAT was detected predominantly in the plasma membrane, and quantitative analysis revealed increased DAT density in striatal compared with midbrain plasma membranes. Endosomes were strikingly rare and lysosomes were absent in striatal axons, in which there was little intracellular HA-DAT. Acute administration of amphetamine in vivo (60 min) or to slices ex vivo (10-60 min) did not result in detectable changes in DAT distribution. Altogether, these data provide evidence for regional differences in DAT plasma membrane targeting and retention and suggest a surprisingly low level of endocytic trafficking of DAT in the striatum along with limited DAT endocytic activity in somatodendritic areas.
    Significance statement: The dopamine transporter (DAT) is the key regulator of the dopamine neurotransmission in the CNS. In the present study, we developed a new approach for studying DAT localization and dynamics in intact neurons in acute sagittal brain slices from the knock-in mouse expressing epitope-tagged DAT. For the first time, the fluorescence imaging analysis of DAT was combined with the immunogold labeling of DAT and quantitative electron microscopy. In contrast to numerous studies of DAT trafficking in heterologous expression systems and dissociated cultured neurons, studies in intact neurons revealed a surprisingly low amount of endocytic trafficking of DAT at steady state and after acute amphetamine treatment and suggested that non-vesicular transport could be the main mechanism establishing DAT distribution within the dopaminergic neuron.
    MeSH term(s) Amphetamine/pharmacology ; Animals ; Axons/chemistry ; Axons/ultrastructure ; Cell Compartmentation ; Cells, Cultured ; Corpus Striatum/metabolism ; Corpus Striatum/pathology ; Dopamine/metabolism ; Dopamine Plasma Membrane Transport Proteins/metabolism ; Dopaminergic Neurons/metabolism ; Endocytosis ; Female ; Gene Knock-In Techniques ; HEK293 Cells ; Humans ; Immunohistochemistry ; Male ; Mice ; Mice, Transgenic ; Microscopy, Electron ; Microscopy, Fluorescence ; Protein Transport ; Rats ; Subcellular Fractions
    Chemical Substances Dopamine Plasma Membrane Transport Proteins ; Amphetamine (CK833KGX7E) ; Dopamine (VTD58H1Z2X)
    Language English
    Publishing date 2015-09-12
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 604637-x
    ISSN 1529-2401 ; 0270-6474
    ISSN (online) 1529-2401
    ISSN 0270-6474
    DOI 10.1523/JNEUROSCI.1391-15.2015
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