Understanding the Neurochemical Processes of Risky Decision Making

Risky decision making is a defining feature of several psychiatric conditions, including pathological gambling and substance use disorders. Understanding the neurochemical processes involved in risky decision making is important for developing novel treatment options for those that have a disorder characterized by excessive risk. The goal of the current study was to determine the contribution of the glutamatergic system to risky decision making using an animal model. Glutamate is the major excitatory neurotransmitter in the brain and is heavily involved in learning and memory. Male rats (n = 12) were tested in the risky decision task (RDT). In the RDT, rats were allowed to choose between two rewards. One reward consisted of one food pellet. The other reward consisted of four pellets; however, receiving the larger alternative was paired with a mild foot shock. The probability that rats received the foot shock increased across the session (0, 25, 50, 75, 100%). Once rats learned the task, they received injections of the glutamatergic drugs MK-801 (0, 0.01, 0.03, 0.06 mg/kg) and Ro 63-1908 (0, 0.1, 0.3, 1.0 mg/kg). We found that MK-801 decreased preference for the large, risky option, but it also decreased preference for the large reward when no foot shock was paired with delivery of this alternative (suggesting that MK-801 impairs the animal’s ability to differentiate the small and large rewards as opposed to altering risky choice per se). Conversely, Ro 63-1908 only marginally decreased preference for the large, risky option, but it did not affect preference for this reward when rats did not receive a foot shock. These results suggest that glutamatergic drugs may not be efficacious in treating risk-based disorders, such as pathological gambling and substance use disorders