Date of Award

Spring 2023

Degree Type




Director of Thesis

Dr. Peter Vento

First Reader

Dr. Neil Levens

Second Reader

Dr. Neil Levens


Previous studies have shown that within the nucleus accumbens (NAc), a brain region associated with motivation and reinforcement learning, activity of neurons expressing the dopamine D2 receptor (D2R neurons) act as a “break” on risky behavior associated with negative outcomes. Moreover, when these neurons are stimulated, rats were found to become more risk averse. However, the impact of dopamine signaling through NAc D2R neurons in risk avoidance is still unclear. To further explore the role of NAc dopamine signaling in punished reward-seeking, we tested rats in a novel punished food-seeking paradigm in which subjects are trained to choose between a large (3 pellet) food reward immediately followed by brief mild foot shock, or to rather make unpunished responses for a smaller (1 pellet) “safe” reward option. Specifically, we completed a pharmacological study investigating the impact of the D2 agonist quinpirole, microinfused bilaterally directly into the NAc, on rats' willingness to endure punishment to receive the large (punished) reward option. Given the established role for NAc D2R neurons in “risky” behavior, we hypothesized that injecting a D2 receptor agonist into the NAc would cause persistent reward seeking despite punishment. Preliminary results, however, show negligible effects of quinpirole on punishment sensitivity. While further testing is needed, these preliminary findings suggest NAc D2 receptor activation is not sufficient to induce punishment resistance, and perhaps instead activation of other NAc cell types such as D1-expressing neurons, or recruitment of other brain regions like the prefrontal cortex, may be involved in suppressing punished responding for food.

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© 2023, Grace M Joyner and Anna Caroline Toburen