Intravenous heroin self-administration decreases GABA efflux in the ventral pallidum: an in vivo microdialysis study in rats.
Eur J Neurosci. 2004-07-01; 20(2): 593-596
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1. Eur J Neurosci. 2004 Jul;20(2):593-6.
Intravenous heroin self-administration decreases GABA efflux in the ventral
pallidum: an in vivo microdialysis study in rats.
Caillé S(1), Parsons LH.
(1)Department of Neuropharmacology, CVN-7, The Scripps Research Institute, 10550
North Torrey Pines Road, La Jolla, CA 92037, USA.
Several lines of evidence suggest that opiate-induced disinhibition of the
ventral pallidum participates in the mediation of opiate reward, though direct in
vivo evidence to support this hypothesis has been lacking. The present experiment
tested this hypothesis by investigating alterations in ventral pallidal amino
acid efflux using in vivo microdialysis during ongoing intravenous heroin
self-administration in rats. Concentrations of the inhibitory amino acid GABA in
ventral pallidal dialysates were significantly reduced within the first 10 min of
heroin self-administration (0.02 mg per infusion; FR-1), and remained
approximately 65% of presession baseline levels for the remainder of the 3-h
self-administration session. Dialysate glutamate levels were unaltered during the
first hour of heroin intake but significantly increased to a stable level of
approximately 120% presession values during the subsequent 2 h of
self-administration. Thus, heroin self-administration is associated with both
decreased GABA efflux and a late phase increase in glutamate efflux in the
ventral pallidum. These observations are consistent with the hypothesis that
heroin self-administration results in a disinhibition and/or excitation of the
PMID: 15233770 [Indexed for MEDLINE]