EFFECT OF NICOTINE ADMINISTRATION ON THE EXPRESSION OF ENKEPHALIN AND DELTA-OPIOID RECEPTOR (DOR) mRNA OF THE RAT BRAIN
Project no. 1077 · Status: Kapanmış · 2016
Summary
Delta opioid receptors (DOR) and their endogenous ligands, proenkephalin (PENK) -derived opioid peptides are proposed as important mediators of nicotine reward. This study investigated the regulatory effect of chronic nicotine treatment on the gene expression of DOR and PENK in the mesocorticolimbic system. Three groups of rats were injected subcutaneously with nicotine at doses of 0.2, 0.4, or 0.6 mg/kg/day for 6 days. Rats were decapitated 1 hr after the last dose on day six, as this timing coincides with increased dopamine release in the mesocorticolimbic system. mRNA levels in the ventral tegmental area (VTA), lateral hypothalamic area (LHA), amygdala (AMG), dorsal striatum (DST), nucleus accumbens (NAc), and medial prefrontal cortex (mPFC) were measured by quantitative real-time PCR. Our results showed that nicotine upregulated DOR mRNA in the VTA at all of the doses employed, in the AMG at the 0.4 and 0.6 mg/kg doses, and in the DST at the 0.4 mg/kg dose. Nicotine did not regulate PENK mRNA in any brain region studied.