Direct-Pathway Striatal Neurons Regulate the Retention of Decision-Making Strategies

The dorsal striatum has been implicated in reward-based decision making, but the role played by specific striatal circuits in these processes is essentially unknown. Using cell phenotype-specific viral vectors to express engineered G-protein-coupled DREADD (designer receptors exclusively activated by designer drugs) receptors, we enhanced G(i/o)- or G(s)-protein-mediated signaling selectively in direct-pathway (striatonigral) neurons of the dorsomedial striatum in Long–Evans rats during discrete periods of training of a high versus low reward-discrimination task. Surprisingly, these perturbations had no impact on reward preference, task performance, or improvement of performance during training. However, we found that transiently increasing G(i/o) signaling during training significantly impaired the retention of task strategies used to maximize reward obtainment during subsequent preference testing, whereas increasing G(s) signaling produced the opposite effect and significantly enhanced the encoding of a high-reward preference in this decision-making task. Thus, the fact that the endurance of this improved performance was significantly altered over time—long after these neurons were manipulated—indicates that it is under bidirectional control of canonical G-protein-mediated signaling in striatonigral neurons during training. These data demonstrate that cAMP-dependent signaling in direct-pathway neurons play a well-defined role in reward-related behavior; that is, they modulate the plasticity required for the retention of task-specific information that is used to improve performance on future renditions of the task

Transient neuronal inhibition reveals opposing roles of indirect and direct pathways in sensitization

The dorsal striatum plays an important role in the development of drug addiction; however, a precise understanding of the roles of striatopallidal (indirect) and striatonigral (direct) pathway neurons in regulating behaviors remains elusive. Using a novel approach that relies on the viral-mediated expression of an engineered GPCR (hM4D), we demonstrated that activation of hM4D receptors with clozapine-N-oxide (CNO) potently reduced striatal neuron excitability. When hM4D receptors were selectively expressed in either direct or indirect pathway neurons in rats, CNO did not change acute locomotor responses to amphetamine but altered behavioral plasticity associated with repeated drug treatment. Specifically, transiently disrupting striatopallidal neuronal activity facilitated behavioral sensitization whereas decreasing excitability of striatonigral neurons impaired its persistence. These findings suggest that acute drug effects can be parsed from the behavioral adaptations associated with repeated drug exposure and highlight the utility of this approach for deconstructing neuronal pathway contributions to behaviors such as sensitization

Protracted Withdrawal from Cocaine Self-Administration Flips the Switch on 5-HT1B Receptor Modulation of Cocaine Abuse-Related Behaviors

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