In vivo evidence that 5-HT2C receptor antagonist but not agonist modulates cocaine-induced dopamine outflow in the rat nucleus accumbens and striatum.
During recent years, much attention has been devoted at investigating the modulatory role of central 5-HT(2C) receptors on dopamine (DA) neuron activity, and it has been proposed that these receptors modulate selectively DA exocytosis associated with increased firing of DA neurons. In the present study, using in vivo microdialysis in the nucleus accumbens (NAc) and the striatum of halothane-anesthetized rats, we addressed this hypothesis by assessing the ability of 5-HT(2C) agents to modulate the increase in DA outflow induced by haloperidol and cocaine, of which the effects on DA outflow are associated or not with an increase in DA neuron firing, respectively. The intraperitoneal administration of cocaine (10-30 mg/kg) induced a dose-dependent increase in DA extracellular levels in the NAc and the striatum. The effect of 15 mg/kg cocaine was potentiated by the mixed 5-HT(2C/2B) antagonist SB 206553 (5 mg/kg i.p.) and the selective 5-HT(2C) antagonist SB 242084 (1 mg/kg i.p.) in both brain regions. The mixed 5-HT(2C/2B) agonist, Ro 60-0175 (1 mg/kg i.p.), failed to affect cocaine-induced DA outflow, but reduced significantly the increase in DA outflow induced by the subcutaneous administration of 0.1 mg/kg haloperidol. The obtained results provide evidence that 5-HT(2C) receptors exert similar effects in both the NAc and the striatum, and they modulate DA exocytosis also when its increase occurs independently from an increase in DA neuron impulse activity. Furthermore, they show that 5-HT(2C) agonists, at variance with 5-HT(2C) antagonists, exert a preferential control on the impulse-stimulated release of DA.
Navailles
Sylvia
S
UMR CNRS, 5541-Université Victor Segalen Bordeaux 2, Bordeaux Cedex, France.
De Deurwaerdère
Philippe
P
Porras
Grégory
G
Spampinato
Umberto
U
D000631:Aminopyridines / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003042:Cocaine / Q000494:pharmacology*; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D018492:Dopamine Antagonists / Q000494:pharmacology; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004347:Drug Interactions; D004563:Electrochemistry / Q000379:methods; D005021:Ethylamines / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006220:Haloperidol / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D017551:Microdialysis / Q000379:methods; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044405:Receptor, Serotonin, 5-HT2C / Q000378:metabolism*; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D013997:Time Factors
C107820:6-chloro-5-methyl-1-((2-(2-methylpyrid-3-yloxy)pyrid-5-yl)carbamoyl)indoline; D000631:Aminopyridines; D018492:Dopamine Antagonists; D018765:Dopamine Uptake Inhibitors; D005021:Ethylamines; D007211:Indoles; D011725:Pyridines; D044405:Receptor, Serotonin, 5-HT2C; C103848:Ro 60-0175; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; C094868:SB 206553; D003042:Cocaine; D006220:Haloperidol; D004298:Dopamine