Abstract
Previous research shows that nicotine increases dopamine (DA) clearance in rat prefrontal cortex (PFC) and striatum via a nicotinic receptor (nAChR)-mediated mechanism. The present study investigated whether activation of nAChRs regulates DA transporter (DAT) function through a trafficking-dependent mechanism. After nicotine administration (0, 0.3, and 0.8 mg/kg s.c., 15-1440 min after injection), DAT function and trafficking in synaptosomes of PFC and striatum were determined. nAChR mediation of the effect of nicotine on DAT function and trafficking in PFC was determined by pretreatment with mecamylamine, dihydro-β-erythroidine, or methyllycaconitine. Nicotine (0.8 mg/kg, 15 and 30 min after injection) increased the maximal velocity (Vmax) of [3H]DA uptake in PFC with no change in Km, compared with control. Biotinylation and Western blot assays showed that nicotine (0.8 mg/kg; 30 min) increased DAT cell surface expression in PFC. In contrast, a lower dose of nicotine (0.3 mg/kg; 30 min) did not alter DAT function and trafficking in PFC. Pretreatment with mecamylamine, dihydro-β-erythroidine, or methyllycaconitine (1.5, 8.0, and 10.0 mg/kg s.c., respectively) completely blocked the nicotine-induced increase in Vmax in PFC. In addition, mecamylamine completely blocked the nicotine-induced increase in DAT cell surface expression in PFC. Nicotine did not increase DAT function and cell surface expression in striatum, indicating that nicotine modulates DAT function in a brain region-specific manner. Thus, results from the present study suggest that the nicotine-induced increases in DAT function and cell surface expression in PFC may mediate some of the behavioral effects of nicotine.
Footnotes
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This study was supported by the National Institutes of Health National Institute on Drug Abuse [Grant DA-018372].
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doi:10.1124/jpet.108.147025.
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ABBREVIATIONS: DA, dopamine; nAChR, nicotinic acetylcholine receptor; DAT, dopamine transporter; NAc, nucleus accumbens; PFC, prefrontal cortex; PP2A, protein phosphatase 2A; HRP, horseradish peroxidase; sulfo-NHS-biotin, sulfosuccinimidobiotin; MLA, methyllycaconitine; DHβE, dihydro-β-erythroidine; [3H]WIN 35,428, (-)-3β-(4-fluorophentl)-tropan-2β-carboxylic acid methyl ester tartrate; mPFC, medial prefrontal cortex; NET, norepinephrine transporter; SERT, serotonin transporter; GBR 12909, 1-{2-[bis-(4-fluorophenyl)methoxy]ethyl}-4-(3-phenylpropyl)piperazine; PBS, phosphate-buffered saline; ANOVA, analysis of variance.
- Received October 5, 2008.
- Accepted December 15, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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