An in vivo microdialysis characterization of extracellular dopamine and GABA in dorsolateral striatum of awake freely moving and halothane anaesthetised rats

P. G. Osborne, W. T. O'Connor, K. L. Drew, U. Ungerstedt

Research output: Contribution to journalArticlepeer-review

Abstract

This study describes the results of a systematic characterization of extracellular dopamine (DA) and γ-aminobutyric acid (GABA) recovered from dorsolateral striatum using in vivo microdialysis in rats following acute (2.5 h) and chronic (1 day, 2 day and 4 day) implantation of the probe. The voltage and calcium dependence of DA and GABA overflow was characterised by perfusion with the sodium channel blocker tetrodotoxin (TTX 10-6M) and with Ca2+-free Ringers perfusion medium. In addition, the effect of halothane anaesthesia on the responsiveness of these neurotransmitter substances to TTX and Ca2+-free perfusion medium was investigated. Perfusion with TTX decreased basal DA levels by at least 60% in all groups. The TTX-induced decrease was most profound in halothane-anaesthetised rats, 24 h after implantation of the probe. Responsiveness of GABA to TTX infusion was different between the groups. In acutely implanted halothane-anaesthetised rats basal GABA levels were unaltered by perfusion with TTX while in the remaining groups at least a 35% reduction was observed. In awake rats 2 days following implantation of the probe removal and replacement of the Ca2+ from the perfusion medium resulted in a reversible reduction of basal DA by 87%. In addition, basal GABA levels were decreased by 52%. This decrease was delayed and was not reversed 1.5 h after the Ca2+-free perfusion medium was replaced with normal perfusion medium although basal GABA levels returned to pre-experimental levels by the following day. The present study demonstrates that the responsiveness of striatal DA and GABA to manipulations of both voltage-dependent (TTX) and vesicular release (Ca2+-free perfusion) is influenced by the length of time elapsed after the implantation of the dialysis fiber and the conscious state of the animal.

Original languageEnglish
Pages (from-to)99-105
Number of pages7
JournalJournal of Neuroscience Methods
Volume34
Issue number1-3
DOIs
Publication statusPublished - Sep 1990
Externally publishedYes

Keywords

  • Calcium
  • Dopamine
  • GABA
  • Microdialysis
  • TTX

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