Does testosterone suppress dopamine in nucleus accumbens during decision making?
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Introduction: Anabolic-androgenic steroids (AAS) are derivates from the hormone testosterone and are mainly used to enhance muscle mass and athletic performance. There are some negative behavioral effects associated with AAS abuse such as increased aggression and physical risk taking. The nucleus accumbens (Acb) is a region of the mesolimbic dopamine system involved in reward, motivated behavior and decision making. Testosterone may influence risk taking and decision making behavior by altering dopamine function in Acb.
Aim: The aim was to investigate whether the hormone testosterone affects dopamine (DA) levels in nucleus accumbens during decision making in male rats.
Materials and Methods: Eight male Long Evans rats were treated with high dose testosterone (7.5 mg/kg) or vehicle (control group). They were tested daily on a probability discounting task where they chose between a small, certain reward (1 pellet delivered 100% of the time) and a large, uncertain reward (4 pellets) delivered with decreasing probability within the blocks (100, 75, 50, 25 and 0%). When choice performance was stable they underwent surgery to implant a cannula in the Acb. After recovery, microdialysis was performed on behaving rats with the aim of measuring DA levels in Acb during decision making.
Results: In probability discounting there was a significant effect of drug on selection of the large reward, with testosterone-treated rats choosing the large reward less compared to the controls. The results for dopamine levels in Acb are still preliminary. We anticipate that dopamine correlates with risk taking as confirmed in previous studies.
Conclusions: Testosterone decreases risk taking in probability discounting. However, the question of testosterone's effect on Acb DA during decision making cannot be answered at this time.
Place, publisher, year, edition, pages
2015. , 25 p.
testosterone, risktaking, risk-averse, desicion making, dopamine
IdentifiersURN: urn:nbn:se:uu:diva-275804OAI: oai:DiVA.org:uu-275804DiVA: diva2:901289
University of Southern California
Subject / course
Master of Science Programme in Pharmacy
Wood, Ruth, ProfessorWallin, Kathryn G
Hallberg, Mathias, Docent