Involvement of intrinsic cholinergic and GABAergic innervation in the effect of NMDA on striatal dopamine efflux and metabolism as assessed by microdialysis studies in freely moving rats

Authors

  • K. J. Whitehead,

    Corresponding author
    • * Correspondence and present address: Dr K. J. Whitehead, Department of Pharmacology, Division of Neuroscience, The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
      E-mail: k.j.whitehead@bham.ac.uk

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  • S. Rose,

    1. Neurodegenerative Diseases Research Centre, Hodgkin Building, Guy's, King's and St Thomas's School of Biomedical Sciences, King's College, Guy's Campus, London SE1 1UL, UK
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  • P. Jenner

    1. Neurodegenerative Diseases Research Centre, Hodgkin Building, Guy's, King's and St Thomas's School of Biomedical Sciences, King's College, Guy's Campus, London SE1 1UL, UK
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Abstract

Microdialysis perfusion was used to study the participation of striatal cholinergic and γ-aminobutyric acid-ergic (GABAergic) neurotransmission in basal and N-methyl-d-aspartate (NMDA) receptor-modulated dopamine release and metabolism in the striatum of the freely moving rat. Reverse dialysis of atropine (1–50 µm) induced a concentration-related increase in dopamine efflux and decrease in 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) efflux. (+)-Bicuculline (10–100 µm) similarly increased dopamine efflux, but was without consistent effect on metabolite efflux. Reverse dialysis of NMDA (1 mm) evoked an approximately twofold increase in dopamine efflux and decreased DOPAC and HVA efflux to 30–40% of basal levels. The effect of NMDA on dopamine efflux was completely abolished by coadministration of tetrodotoxin (TTX; 1 µm) or atropine (10 µm), and markedly potentiated (approximately fourfold) by coadministration of (+)-bicuculline (50 µm). The NMDA-induced decrease in dopamine metabolite efflux was inhibited by coadministration of TTX or (+)-bicuculline, but was unaffected by atropine. Our data suggest that dopamine release in the striatum is subject to both cholinergic and GABAergic tonic inhibitory mechanisms mediated through muscarinic and GABAA receptors, respectively. Furthermore, NMDA-stimulated dopamine release also involves obligatory cholinergic facilitation and an inhibitory GABAergic component mediated through these respective receptors.

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