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Chronic nicotine modifies the effects of morphine on extracellular striatal dopamine and ventral tegmental GABA
Author(s) -
Vihavainen Tanja,
Relander Toni R. A.,
Leiviskä Riikka,
Airavaara Mikko,
Tuominen Raimo K.,
Ahtee Liisa,
Piepponen Timo Petteri
Publication year - 2008
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2008.05676.x
Subject(s) - ventral tegmental area , nucleus accumbens , dopaminergic , dopamine , nipecotic acid , nicotine , gabaergic , medicine , chemistry , microdialysis , endocrinology , substantia nigra , pharmacology , neurotransmitter , central nervous system , receptor
Abstract Previously, we have shown that 7‐week oral nicotine treatment enhances morphine‐induced behaviors and dopaminergic activity in the mouse brain. In this study, we further characterized the nicotine‐morphine interaction in the mesolimbic and nigrostriatal dopaminergic systems, as well as in the GABAergic control of these systems. In nicotine‐pretreated mice, morphine‐induced dopamine release in the caudate putamen and nucleus accumbens was significantly augmented, as measured by microdialysis. Chronic nicotine treatment did not change basal extracellular concentrations of dopamine and its metabolites in the caudate putamen and nucleus accumbens, nor did it affect the rate of dopamine synthesis, as assessed by 3‐hydroxybenzylhydrazine dihydrochloride‐induced DOPA accumulation. GABAergic control of dopaminergic activity was studied by measuring extracellular GABA in the presence of nipecotic acid, an inhibitor of GABA uptake. Acute (0.3 mg/kg or 0.5 mg/kg i.p.) and chronic nicotine, as well as morphine (15 mg/kg s.c.) in control mice decreased nipecotic acid–induced increase in extracellular GABA in the ventral tegmental area/substantia nigra (VTA/SN). In contrast, in nicotine‐treated mice, morphine increased GABA levels in the presence of nipecotic acid. We did not find any alterations in GABA B ‐receptor function after chronic nicotine treatment. Thus, our data show that chronic nicotine treatment sensitizes dopaminergic systems to morphine and affects GABAergic systems in the VTA/SN.