An Interaction between Serotonin Receptor Signaling and Dopamine Enhances Goal-Directed Vigor and Persistence in Mice

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Motivated behaviors are crucial for survival and are influenced by reward, effort, and cost-benefit analyses.
• Dopamine (DA) signaling regulates key aspects of motivated behavior, making it challenging to selectively modulate specific components.
• Apathy and motivational deficits are significant clinical challenges in various psychiatric and neurological disorders.

Purpose of the Study:

• To investigate the specific behavioral effects of the 5-HT2C receptor ligand SB242084 in female and male mice.
• To elucidate the neurobiological mechanisms underlying SB242084's effects on motivated behavior.
• To explore the potential of SB242084 as a therapeutic agent for apathy.

Main Methods:

• Quantitative behavioral analysis to assess vigor and persistence of goal-directed activity.
• In vivo fast scan cyclic voltammetry to measure DA release in the nucleus accumbens (NAc).
• In vivo microdialysis to measure tonic extracellular DA levels in the NAc and dorsomedial striatum.

Main Results:

• SB242084 significantly increased the vigor and persistence of goal-directed activity, particularly under demanding conditions.
• SB242084 did not affect reward-related phasic DA release or tonic DA levels in the NAc.
• SB242084 treatment elevated extracellular DA in the dorsomedial striatum, a region critical for response vigor.

Conclusions:

• SB242084 enhances motivated behavior by selectively potentiating DA release in the dorsomedial striatum, independent of reward value or generalized motor activity.
• This study identifies a specific serotonin receptor-dopamine system interaction that modulates effort-based decision-making.
• The findings suggest a promising therapeutic strategy for treating apathy and related motivational deficits.