Nicotine regulates cocaine-amphetamine-Regulated Transcript (Cart) in the mesocorticolimbic system

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ABSTRACTCocaine-and-Amphetamine Regulated Transcript (CART) mRNA and peptides are intensely expressed in the brain regions comprising mesocorticolimbic system. Studies suggest that CART peptides may have a role in the regulation of reward circuitry. The present study aimed to examine the effect of nicotine on CART expression in the mesocorticolimbic system. Three different doses of nicotine (0.2, 0.4, 0.6 mg/kg free base) were injected subcutaneously for 5 days, and on day 6, rats were decapitated following a challenge dose. CART mRNA and peptide levels in medial prefrontal cortex (mPFC), nucleus accumbens (NAc), dorsal striatum (DST), amygdala (AMG), lateral hypothalamic area (LHA), and ventral tegmental area (VTA) were measured by quantitative real-time PCR (qPCR) and Western Blot analysis, respectively. In the mPFC, 0.4 and 0.6 mg/kg nicotine, decreased CART peptide levels whereas there was no effect on CART mRNA levels. In the VTA, a down-regulation of CART peptide expression was observed with 0.2 and 0.6 mg/kg nicotine. Conversely, 0.4 and 0.6 mg/kg nicotine increased CART mRNA levels in the AMG without affecting the CART peptide expression. Nicotine did not regulate CART mRNA or CART peptide expression in the NAc, DST, and LHA. We conclude that nicotine regulates CART expression in the mesocorticolimbic system and this regulation may play an important role in nicotine reward.Western Blot and qPCR analysis showed that nicotine (0.2, 0.4, 0.6 mg/kg, sc) administration for 6 days regulated CART peptide and mRNA expression in the rat mesocorticolimbic system.

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