Concurrent measures of impulsive action and choice are partially related and differentially modulated by dopamine D1- and D2-like receptors in a rat model of impulsivity

Abstract

Impulsivity is a multidimensional construct, but the relationships between its constructs and their respective underlying dopaminergic underpinnings in the normal population remain unclear. A large cohort of Roman high-(RHA) and low- (RLA) avoidance rats were tested for impulsive action and risky decision-making in the rat gambling task, and then for delay discounting in the delay discounting task to concurrently measure the relationships among the three constructs of impulsivity using a within-subject design. Then, we evaluated the effects of dopaminergic drugs on the three constructs of impulsivity, considering innate differences in impulsive behaviors at baseline. Risky decision-making and delay discounting were positively correlated, indicating that both constructs of impulsive choice are related. Impulsive action positively correlated with risky decision-making but not with delay discounting, suggesting partial overlap between impulsive action and impulsive choice. RHAs showed a more impulsive phenotype in the three constructs of impulsivity compared to RLAs, demonstrating the comorbid nature of impulsivity in a normal population. While amphetamine increased impulsive action and had no effects on risky decision-making regardless of baseline levels of impulsivity, it decreased delay discounting but only in high impulsive RHAs. Conversely, the D1R agonist SKF81297, D3R agonist PD128907 and D2/3R partial agonist aripiprazole decreased impulsive action irrespective of baseline levels of impulsivity, whereas D2/3R agonism with quinpirole decreased it exclusively in high impulsive RHAs. Risky decision-making was increased by SKF81297 and quinpirole but not PD128907 and aripiprazole, with quinpirole producing baseline-dependent effects, increasing risky decision-making only in low impulsive RLAs. Finally, while SKF81297, PD128907 and aripiprazole increased delay discounting irrespective of baseline levels of impulsivity, quinpirole decreased it in low impulsive RLAs only. These findings indicate that the acute effects of dopamine drugs were partially overlapping across dimensions of impulsivity, and that only D2/3R agonism showed baseline-dependent effects on the three constructs of impulsivity.