Long-lasting Avoidance Induced by Repeated Stimulation of the Rostromedial Tegmental Nucleus

Adaptive decision-making requires the ability to weigh the relative costs versus the benefits of our actions and to flexibly respond to changing environmental contingencies. While midbrain dopamine (DA) has been a major focus of study for its role in associative learning, motivation, and reward seeking, far less is known regarding the contribution of inhibitory dopamine inputs in promoting behavioral inhibition and avoidance learning. The rostromedial tegmental nucleus (RMTg) sends dense GABAergic projections to DA neurons in the ventral tegmental area (VTA) and mounting evidence suggests the RMTg-VTA circuit is required to suppress reward seeking under punishment, but it remains unclear whether stimulation of this pathway is sufficient to drive learning and promote shifts in cost-benefit decisions. To test this, we developed two separate tasks of passive and active avoidance in rats where lever pressing for food reward was associated with repeated contingent optogenetic stimulation of the RMTg-VTA pathway. In a one-lever fixed ratio 5 food-seeking task, we found that pairing RMTg-VTA stimulation with reward delivery caused a robust, yet transient suppression of reward seeking that quickly returned to baseline after contingent stimulation ceased. When given an alternative reward choice, however, RMTg-VTA stimulation caused a rapid and enduring shift in subjective choice leading to persistent and selective avoidance of the stimulation-paired reward. These findings support a multifaceted role for the RMTg-VTA pathway in learning and decision-making and provide key insights into the neural mechanisms underlying behavioral avoidance and maladaptive reward seeking.