The reward system is a set of neuronal structures responsible for the processing of a number of psychological components, such as 'wanting', 'liking' and associative learning (Berridge & Robinson, 2003).These three processes occur together, 'wanting' dominates the initial appetitive phase, 'liking' dominates the consummatory phase, and learning occurs through the reward-behavioural cycle (Berridge et al., 2016). Both phenomena are underpinned by different brain circuits and neurotransmitter systems. The 'wanting' component is largely controlled by the dopaminergic system, whereas the 'liking' component is thought to be more mediated by opioid and GABAergic systems (Berridge & Robinson, 2003). The neural circuitry constituting the anatomical and neurochemical substrate for reward and pleasure was described several decades ago by Olds and Milner, who, after implanting electrodes in certain areas of the central nervous system (CNS) and administering electrical microstimuli, demonstrated a pleasure response in the animals (Olds and Milner 1954).Following this, it was proposed that the monoaminergic activity could underlie the neurochemical basis of pleasure, with the monoaminergic system playing an important role in drug reinforcement