Author(s): Marcenac F, Jin GZ, Gonon F
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Abstract In vivo voltammetric measurements of striatal extracellular DOPAC concentrations and of striatal DA release in combination with post-mortem analysis of striatal catechols were performed in the rat to study the effects on the nigro-striatal neurons of a Chinese neuroleptic, l-tetrahydropalmatine (l-THP), which is known to block post-synaptic dopaminergic receptors. l-THP injected at doses that cause sedation in rats and mice (5-10 mg/kg) induced a marked increase in post-mortem DOPAC levels (+250\%), while no significant effect was observed on postmortem DA levels. The extracellular DOPAC concentration was increased to 155 +/- 9\% of the control value after l-THP administration (1 mg/kg, IP). Further, an injection of l-THP (1 mg/kg, IP) induced an increase in extracellular DA concentration (220\% of the basal value), reversed the decrease in extracellular DA concentration induced by apomorphine (0.05 mg/kg, SC) and enhanced the effects of the electrical stimulation of the nigro-striatal pathway. These results confirm that l-THP acts on the nigro-striatal neurons as a dopaminergic antagonist that can block both post- and presynaptic receptors.
This article was published in Psychopharmacology (Berl)
and referenced in Medicinal & Aromatic Plants