Modulatory Effect of Dopamine on High-Affinity Glutamate Uptake in the Rat Striatum

Authors

  • Lydia Kerkerian,

    Corresponding author
    1. Unité de Neurochimie, Laboratoire de Neurosciences Fonctionnelles du CNRS, Marseille, France
      Address correspondence and reprint requests to Dr. L. Kerkerian at Unité de Neurochimie, Laboratoire de Neurosciences Fonctionnelles du CNRS, BP 71, 13402 Marseille cedex 9, France.
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  • Nicole Dusticier,

    1. Unité de Neurochimie, Laboratoire de Neurosciences Fonctionnelles du CNRS, Marseille, France
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  • André Nieoullon

    1. Unité de Neurochimie, Laboratoire de Neurosciences Fonctionnelles du CNRS, Marseille, France
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Address correspondence and reprint requests to Dr. L. Kerkerian at Unité de Neurochimie, Laboratoire de Neurosciences Fonctionnelles du CNRS, BP 71, 13402 Marseille cedex 9, France.

Abstract

Abstract: In vivo electrical stimulation of the frontal cortical areas was found to enhance sodium-dependent high-affinity glutamate uptake (HAGU) measured in rat striatal homogenates. This activating effect was counteracted by in vivo administration of apomorphine and by in vitro addition of dopamine (DA; 10–8M) in the incubation medium, and potentiated by in vivo haloperidol administration. At the doses used, the dopaminergic compounds had no effect on basal HAGU. α-Methylparatyrosine pretreatment was found to enhance slightly basal HAGU as well as the activating eifects of cortical stimulation. Interestingly enough, lesion of dopaminergic neurons by substantia nigra injection of 6-hydroxydopamine (6-OHDA) did not cause any significant change either in basal HAGU or in the effect of cortical stimulation. Measurement of DA effects in vitro in experiments combined with in vivo manipulations of the dopaminergic nigrostriatal and corticostriatal systems showed that the capacity of DA to inhibit striatal HAGU depends directly on the level of the uptake activation reached over basal value. These results suggest that under physiological conditions, the dopaminergic nigrostriatal pathway exerts a modulatory presynaptic action on corticostriatal glutamatergic transmission, counteracting increasing glutamatergic activity. In the case of chronic DA depletion induced by 6-OHDA, striatal adaptations may occur modifying the mechanisms acting at corticostriatal nerve terminal level.

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