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A Microdialysis Study of the Regulation of Endogenous Noradrenaline Release in the Rat Hippocampus

Authors

  • D. N. Thomas,

    Corresponding author
    1. Reckitt and Colman Psychopharmacology Unit, School of Medical Sciences, Bristol, Avon, England
      Address correspondence and reprint requests to Dr. D. N. Thomas at Reckitt and Colman Psychopharmacology Unit, School of Medical Sciences, University Walk, Bristol, Avon BS8 1TD, U.K.
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  • R. B. Holman

    1. Reckitt and Colman Psychopharmacology Unit, School of Medical Sciences, Bristol, Avon, England
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Address correspondence and reprint requests to Dr. D. N. Thomas at Reckitt and Colman Psychopharmacology Unit, School of Medical Sciences, University Walk, Bristol, Avon BS8 1TD, U.K.

Abstract

Abstract: In vivo microdialysis was used to investigate the regulation of noradrenaline release in rat hippocampus. Idazoxan, an α2-adrenoreceptor antagonist (1–10 mg/kg), increased noradrenaline release in a dose-dependent manner. Inhibition of noradrenaline uptake by desipramine (0.05–20 μM; via the probe) also increased the extracellular content of the transmitter. In the presence of this increased noradrenaline content (desipramine via the probe), the effect of a low dose of idazoxan (1 mg/kg) was potentiated. Local perfusion of idazoxan (1–500 μM) in the hippocampus also increased noradrenaline release but not to the same extent as following systemic administration. In the presence of desipramine, unlike the systemic injection of idazoxan, local perfusion did not potentiate noradrenaline release. The data are consistent with the regulation of extracellular noradrenaline content in the hippocampus by neuronal uptake and to a lesser extent by presynaptic autoreceptors.

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