Nicotine Infusion in the Wake‐Promoting Basal Forebrain Enhances Alcohol‐Induced Activation of Nucleus Accumbens

Background Nicotine and alcohol co‐abuse is highly prevalent. Recently, we have shown that nicotine infusion in the basal forebrain ( BF ) increases alcohol consumption. As nucleus accumbens ( NA c) is the terminal brain region associated with drug addiction, we hypothesize that nicotine infusion in the BF may enhance alcohol‐induced activation of NA c. Methods Adult male S prague– D awley rats were surgically implanted with bilateral guide cannulas in the BF . Following postoperative recovery, rats were divided into 4 groups: (i) ACSF  +  W group received artificial cerebrospinal fluid ( ACSF ; 500 nl/side) in the BF and systemic water (intragastric [ig]; 10 ml/kg; N  = 5), (ii) ethanol (EtOH) group received ACSF in the BF (500 nl/side) and systemic alcohol (ig; 3 g/kg; N  = 5), (iii) NiC group received nicotine in the BF (75 pmole/500 nl/side) and systemic water (ig; 10 ml/kg; N  = 5), and (iv) NiC + EtOH group received nicotine in the BF (75 pmole/500 nl/side) and systemic alcohol (ig; 3 g/kg; N  = 5). Rats were euthanized 2 hours after treatment to examine c‐Fos expression in the NAc by immunohistochemistry. Results All injections sites were localized in the BF . Two‐way analysis of variance (ig vs. infusion) revealed significant main effects of both treatments (ig and infusion, p  < 0.001) on c‐Fos expression in the NA c shell, but not in the core. Subsequent post hoc test (Bonferroni's) revealed that as compared to ACSF  + W group, c‐Fos expression was significantly increased in the shell of NA c of rats in all 3 (Et OH , NiC, and NiC + Et OH ) groups with maximal increase observed in NiC + Et OH group. Conclusions The results suggest the following: (i) BF nicotine infusion induced c‐Fos in both core and the shell region of NA c at levels comparable to those observed after systemic alcohol administration; (ii) BF nicotine infusion with systemic alcohol induced a significant additive increase in c‐Fos expression only in the NA c shell region. These findings implicate the BF in alcohol and nicotine co‐use.