Involvement of noradrenergic and serotonergic systems in risk-based decisions between options of equivalent expected value in rats.
Risk perception is an important factor that may mediate risk-based decision-making processes regulated by noradrenergic (NA) and serotonergic (5-HT) systems. Most risk-based decision-making models involve complex factors, such as risk perception or reward value, such that the final decision is the result of the interactions among these factors. However, the contribution of risk perception per se in risk decisions has remained unclear. Therefore, in the present study, we made some modifications to the classical probabilistic discounting task (PDT) to focus on the impact of risk perception and noradrenergicserotonergic systems on decision-making behavior. Meanwhile, we conducted an elevated plus-maze (EPM) test to detect the correlation between anxiety and choice behavior. In the current study, rats had to choose between a certain lever that delivered a certain number of pellets and a risky lever that delivered eight pellets in a probabilistic manner (descending 50%, 25%, 12.5% or ascending 12.5%, 25%, 50% of the time). The long-term rewarding values of the two levers were always identical in each block within each session. According to their baseline performances in choosing the risky lever, rats were divided into the risk-prefer group and risk-averse group. The results showed that there was a significant correlation between open arm time in EPM and risky choice for both descending order and ascending order, indicating that highly anxious rats more often preferred the safe option under risk. Pharmacological stimulation of α2-adrenergic receptors via dexmedetomidine (0.01 mgkg) decreased the preference of probabilistic rewards in the risk-prefer group, while blocking α2 receptors by atipamezole (0.3 mgkg) also reduced risky choices. The NA reuptake inhibitor, atomoxetine, increased the preference for risky choices in the risk-prefer group, the effect of which was attained via multiple superimposed doses. Administration of the 5-HT