Noradrenergic Modulation of Primary and Secondary Rewards in Healthy Subjects

We investigated effects of the noradrenergic agent reboxetine (REB) and the antipsychotic amisulpride (AMS) in healthy subjects on erotic stimulus processing. Whereas AMS left sexual functions and neural activations unimpaired, we observed detrimental effects of REB on sexual functions along with attenuated neural activations of emotional, autonomic and motivational components (e.g. within the nucleus accumbens; NAcc) of sexual behavior. To assess the effects of these two agents on neural processing of secondary rewards, we now investigated the same sample by fMRI and an established monetary reward paradigm. 17 healthy males were investigated under REB, AMS and placebo for 7 days each within a double-blind cross-over design. During fMRI, we used an monetary incentive task to explore neural prediction error signals within the NAcc. An ANOVA on reaction times revealed a significant main effect for levels of reward-probability. Here, mean reaction times fastened according to higher reward probability in all treatments. In contrast to diminished sexual function and attenuated neural NAcc-activation under REB during erotic stimulation, we revealed unaffected neural NAcc-activity during secondary rewards. Also here, AMS left neural NAcc-activations and behavioural results unimpaired. We provide evidence of specific alterations of reward system activity by noradrenergic agents towards a dampening of primary reward processing and unimpaired neural processing of secondary rewards.