Testosterone enhances risk tolerance without altering motor impulsivity in male rats

Anabolic androgenic steroids (AAS) increase impulsive and uncontrolled aggressive ('roid rage) in humans and enhance agonistic behavior in animals. However, the underlying mechanisms for MS-induced aggression remain unclear. Potential contributing elements include an increase risk-taking and/or motor impulsivity due to AAS. This study addressed the effects of chronic high-dose testosterone on risk tolerance using a risky decision-making task (ROT) and motor impulsivity with a go/no-go task in operant chambers. Male Long Evans rats were treated for at least 4 weeks with testosterone (7.5 mg/kg) or vehicle beginning in late adolescence. Testosterone was used because it is popular among human MS users. In ROT testing, one lever was paired with delivery of a small "safe" food reward, while the other was paired with a large "risky" reward associated with an increasing risk of footshock (0%, 25%, 50%, 75%, 100%) in successive test blocks. Three shock intensities were used: 1.0, 1.2, and 1.4 mA/kg. As shock intensity and risk of shock increased, preference for the lever signifying a large reward significantly declined for both vehicle- and testosterone-treated rats (p < 0.05). There was also a significant effect of drug (p < 0.05), where testosterone-treated rats showed greater preference for the large reward, compared to vehicle-treated controls. Increased preference for the large reward, despite risk of footshock, is consistent with increased risk tolerance. In go/no-go testing, rats were trained to press a single lever if the go cue was presented (stimulus light) or to refrain from pressing during the no-go cue (tone). There was no effect of testosterone on pre-cue responses, or performance in go and no-go trials. These results suggest that MS may increase risk-tolerance without altering motor impulsivity. (C) 2013 Elsevier Ltd. All rights reserved.