The bold-shy continuum: exploring the relationship between personality traits and substance use disorders

Abstract

The United Nations Office on Drugs and Crime (UNODC) reports that alcohol and tobacco are among the most harmful substances globally, with alcohol causing 3 million deaths annually and tobacco responsible for more than 8 million. Both alcohol and nicotine affect the central nervous system, interacting with its neurotransmission to cause its effects. However, not all individuals respond the same to these substances, there are genetic, physiological and psychological aspects that influence how subjects respond to drugs. Some individuals are more sensitive than others. To understand these variations, comparative studies between individuals’ profiles are required, involving individuals with different behavioural and physiological characteristics, to provide valuable information on the basis of different responses to drugs. To better understand the effects of these two additive substances on individual differences, we propose using the zebrafish (Danio rerio) as an animal model. The zebrafish is a vertebrate that has become an important model organism for neuropharmacological and behavioural research in recent decades due to its suitability for studying the effects of neuroactive drugs and inter-individual variation, as distinct behavioural and physiological phenotypes are well established. This model offers the possibility of translational conclusions, as it shows brain biochemical pathways, neurotransmitters and circuitry that have been evolutionarily conserved in humans, making it proper for comparison. Thus, this thesis aimed to evaluate the behavioural, cognitive responses, and gene expression resulting from acute exposure to alcohol and nicotine in zebrafish from different behavioural profiles. Our findings indicate that individual differences rely on context, drug concentration, and behavioural profile, emphasizing the need to consider these variations when evaluating the potential treatments for addictive substances.