Recent studies have demonstrated that anabolic-androgenic steroids (AAS) modify cognitive processes such as decision making and behavioral flexibility. However, the neural mechanisms underlying these AAS-induced cognitive changes remain poorly understood. The mesocorticolimbic dopamine (DA) system, particularly the nucleus accumbens (Acb), is important for reward, motivated behavior, and higher cognitive processes such as decision making. Therefore, AAS-induced plasticity in the DA system is a potential structural substrate for the observed cognitive alterations. High doses of testosterone (the most commonly-used AAS) increase dendritic spine density in limbic regions including the amygdala and hippocampus. However, effects on Acb are unknown. This was the focus of the present study. Adolescent male Long-Evans rats were treated chronically for 8 weeks with high-dose testosterone (7.5 mg/kg in water with 13% cyclodextrin) or vehicle sc. Brains were stained by Golgi-Cox to analyze neuronal morphology in medium spiny neurons of the shell region of Acb (AcbSh). 8 weeks of testosterone treatment significantly decreased spine density in AcbSh compared to brains of vehicle-treated rats (F1,14 = 5.455, p<0.05). Testosterone did not significantly affect total spine number, dendritic length, or arborization measured by Sholl analysis. These results show that AAS alter neuronal morphology in AcbSh by decreasing spine density throughout the dendritic tree, and provides a potential mechanism for AAS to modify cognition and decision-making behavior.
Anabolic-androgenic steroid (AAS) abuse is implicated in maladaptive decision making such as increased risk taking and problem gambling. Endogenous testosterone correlates with economic risk taking in both the stock market (Coates & Herbert, 2008) and in the laboratory, as measured by the Iowa Gambling Task (Stanton, Liening, & Schultheiss, 2011). Additionally, AAS use has been associated with problem gambling behavior in adolescents (Proimos, DuRant, Pierce, & Goodman, 1998). Thus, AAS may impair economic decision making. However, studies of human AAS users cannot control for preexisting risky behavior or normalize androgen levels. Accordingly, the present study investigated AAS effects on decision making in rats using a novel, balanced rodent model of the IGT. Adolescent male Long-Evans rats were treated chronically with high-dose testosterone (7.5 mg/kg) or vehicle (13% cyclodextrin in water) sc, and trained to work for sugar pellets in an operant chamber equipped with 4 levers, each associated with a different schedule of reward magnitude (number of pellets), probability, and punishment (time-out) duration. By RM-ANOVA, there was a main effect of lever (F3,78 = 25.33, p < .05), such that all rats preferred lever L4 offering a large reward (4 pellets), but with low probability (45%) and a long (35 sec) time-out. There was also a significant interaction of testosterone × lever (F3,78 = 2.78, p < .05), with testosterone increasing preference for L4 and decreasing preference for the other levers, relative to vehicle-treated controls. These data extend our previous findings of altered decision making in AAS-treated rats, and suggest that AAS may alter economic decision making in human users. (PsycINFO Database Record
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