Chemogenetic inhibition of the noradrenergic locus coeruleus promotes the development of risk-taking decisional strategies and selectively enhances motor impulsivity in females

The locus coeruleus noradrenaline (LC-NA) system is a key regulator of arousal, attention, and reward learning. Noradrenaline plays a critical role in impulse control, and recent evidence indicates the importance of noradrenaline signaling in cost-benefit decision making once choice strategies are established. However, whether the LC causally shapes the acquisition of decision strategies, and how this contribution may differ across sexes, remains unclear. We addressed these questions by chemogenetically inhibiting catecholaminergic neurons within the LC of adult tyrosine-hydroxylase Cre (TH::Cre) rats (n=69; 35 females) throughout acquisition of the cued rat gambling task (crGT), a probabilistic decision making paradigm that incorporates salient audiovisual reward-paired cues and simultaneously measures motor impulsivity. LC inhibition accelerated the development of risky choice strategies early in training in both males and females, reflected by impaired adoption of the most advantageous option and increased preference for risky options. Trial-by-trial analyses reveal that LC inhibition promoted switches in choice strategy following safe wins, while reducing switches away from risky options after both wins and losses. LC inhibition therefore seemed to encourage the repetition of actions that resulted in more uncertain outcomes. LC inhibition also selectively enhanced motor impulsivity in females, particularly early in training. These results provide causal evidence that the LC system guides the formation of optimal decisional strategies, while exerting sex-specific control over impulsive action.