Together but opposites in reward

Abstract

Dopamine and serotonin may oppositely modulate associative learning, yet their precise roles have not been examined simultaneously in individual animals. Writing in Nature, Cardozo Pinto et al. used a double transgenic approach to genetically access both dopaminergic and serotonergic neurons in mice during a Pavlovian reward conditioning task. Notably, dopamine axonal activity in the ventral striatum increased, whereas serotonin axonal activity decreased, in response to reward; a similar pattern was observed for dopamine and serotonin indicator signals. Optogenetic blunting of either the increase in dopamine axon activity or the decrease in serotonin axon activity did not substantially impair learning, but double blunting of the responses did, which suggests that the coordinated inverse signals are necessary for reward learning. Conditioned learning could be induced by simultaneous optogenetic activation and silencing of dopamine and serotonin axon activity, respectively, more strongly than with either of the manipulations alone. These results suggest that striatal dopamine and serotonin act together, with opposite responses, to modulate reward learning.

Original reference: Nature https://doi.org/10.1038/s41586-024-08412-x (2024)