Differential Dopamine Regulation of Ca2+ Signaling and Its Timing Dependence in the Nucleus Accumbens

• Dopamine transients facilitate IP3-evoked Ca2+ signals within ∼2–10 s
• Dopamine augments spike-evoked Ca2+ signals amplified by the mGluR-IP3 pathway
• D1 dopamine receptors mediate facilitation of IP3-induced Ca2+ signaling
• D2 receptors mediate reversal of A2A adenosine receptor-induced facilitation

SummaryDopamine action in the nucleus accumbens (NAc) is thought to drive appetitive behavior and Pavlovian reward learning. However, it remains controversial how dopamine achieves these behavioral effects by regulating medium spiny projection neurons (MSNs) of the NAc, especially on a behaviorally relevant timescale. Metabotropic glutamate receptor (mGluR)-induced Ca2+ signaling dependent on the Ca2+- releasing messenger inositol 1,4,5-triphosphate (IP3) plays a critical role in controlling neuronal excitability and synaptic plasticity. Here, we show that transient dopamine application facilitates mGluR/IP3-induced Ca2+ signals within a time window of ∼2–10 s in a subpopulation of MSNs in the NAc core. Dopamine facilitation of IP3-induced Ca2+ signaling is mediated by D1 dopamine receptors. In dopamine-insensitive MSNs, activation of A2A adenosine receptors causes enhancement of IP3-evoked Ca2+ signals, which is reversed by D2 dopamine receptor activation. These results show that dopamine differentially regulates Ca2+ signaling on the order of seconds in two distinct MSN subpopulations.

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