Behavioural effects of shoaling on nicotine place preference in zebrafish

Abstract

Nicotine activates the brain´s reward systems leading to addiction. Zebrafish exhibit social behaviours, such asshoaling, making them an attractive model for investigating how social interactions influence behaviour. Here,we assessed the rewarding effects of nicotine on zebrafish shoaling behaviour, examined whether the shoal influencesthe rewarding properties of nicotine. To study shoaling behaviour under drug exposure, we comparednicotine at 15 and 50 mg/L as a reinforcer and a social stimulus through Pavlovian conditioning. Visual interactionof individual zebrafish with a shoal during conditioning or the CPP test was sufficient to decrease nicotine-CPP, spending more time closer to the shoal. We then examined the effect of the shoal during conditioning. Whenfish were conditioned as a group, 15 mg/L of nicotine induced a positive CPP, but 50 mg/L did not. No evidenceof anxiety or stress was found. At 50 mg/L, the distance between zebrafish in the shoal increased, indicating arelaxed behaviour. To better characterize this effect, we exposed the fish to phenylbutyrate (PhB) (an HDACinhibitor) known to reduce nicotine-CPP. In zebrafish conditioned in a shoal, 15 mg/L of nicotine inhibited CPP,but 50 mg/L did not, with reduced interfish distances. Our results indicate that the social environment, such asthe presence of a shoal, can influence nicotine preference in zebrafish, which is significant for understandingsocial influences on addiction in vertebrates, including humans.