Individual differences in response to alcohol and nicotine in zebrafish: gene expression and behavior

Alcohol and nicotine are psychoactive substances responsible for serious health consequences. Although the biological mechanism of alcohol and nicotine have been studied extensively, individual differences in response to these drugs received little attention. Here we evaluated gene expression and behavior of bold and shy individuals after acute exposure to alcohol and nicotine. For this, zebrafish were separated into bold and shy profiles by emergence tests, and then fish were exposed to 0.00, 0.10, and 0.50% alcohol, or 0.00, 1.00, and 5.00 mg/L nicotine and observed for the anxiety-like and locomotor behavior. After behavioral assessment, brain mRNA expression (ache, bdnf, gaba1, gad1b, th1, and tph1) was evaluated. Locomotion patterns differed between profiles depending on alcohol and nicotine concentration. Anxiety increased in shy fish and decreased in bold fish after both drugs exposure. Alcohol exposure induced increase in tph1 mRNA expression in bold fish, while bdnf mRNA expression was increased in shy fish. Nicotine increased ache, bdnf, and tph1 mRNA in both profiles, but at higher levels in bold fish. Based on our research, we found that alcohol induces anxiogenic effects in both bold and shy zebrafish. Additionally, shy individuals exposed to a low concentration of nicotine heightened anxiety-like responses when compared to their bold. These findings further support the validity of using zebrafish as a dependable tool for studying the effects of drugs and uncovering the underlying mechanisms associated with individual variations. This article is protected by copyright. All rights reserved.