High-Frequency Activation of Nucleus Accumbens D1-MSNs Drives Excitatory Potentiation on D2-MSNs

Subtypes of nucleus accumbens medium spiny neurons (MSNs) promote dichotomous outcomes in motivated behaviors. However, recent reports indicate enhancing activity of either nucleus accumbens (NAc) core MSN subtype augments reward, suggesting coincident MSN activity may underlie this outcome. Here, we report a collateral excitation mechanism in which high-frequency, NAc core dopamine 1 (D1)-MSN activation causes long-lasting potentiation of excitatory transmission (LLP) on dopamine receptor 2 (D2)-MSNs. Our mechanistic investigation demonstrates that this form of plasticity requires release of the excitatory peptide substance P from D1-MSNs and robust cholinergic interneuron activation through neurokinin receptor stimulation. We also reveal that D2-MSN LLP requires muscarinic 1 receptor activation, intracellular calcium signaling, and GluR2-lacking AMPAR insertion. This study uncovers a mechanism for shaping NAc core activity through the transfer of excitatory information from D1-MSNs to D2-MSNs and may provide a means for altering goal-directed behavior through coordinated MSN activity. [Display omitted] •High-frequency activation of NAc D1-MSNs causes release of substance P•D1-MSN high-frequency activation potentiates excitatory transmission on D2-MSNs•D1-MSN high-frequency activation drives enhanced cholinergic interneuron firing•D2-MSN AMPA receptor insertion by substance P requires M1 receptor signaling Reward outcomes depend on the stimulation protocol used to activate nucleus accumbens medium spiny neuron (MSN) subtypes. In this issue of Neuron, Francis et al. demonstrate rebalanced MSN subtype excitation driven by high-frequency stimulation and substance P release.