Deep brain live imaging of cAMP and protein kinase A activities underlying synaptic- and circuit-level mechanisms during learned behaviors

Neuromodulation is crucial for information processing throughout the brain. Neuromodulators influence neuronal function by acting through G protein-coupled receptors (GPCRs) to alter neuronal excitability and synaptic transmission, which can then affect circuit functions. GPCRs are major drug targets used to treat a variety of diseases, including neurological disorders. The causal link between in vivo subcellular signaling mechanisms and behaviors is poorly understood due to the limited tools available to monitor signaling in freely behaving animals. Activation of GPCRs stimulates G-protein signaling to increase or decrease cyclic monophosphate (cAMP) accumulation and bidirectionally control Protein Kinase A (PKA) and Exchange Protein directly Activated by cAMP (EPAC) signaling. Although GPCRs are diverse, the downstream second messenger systems are limited. Therefore, the overarching hypothesis of this proposal is that GPCRs decode incoming modulatory inputs by generating distinct spatiotemporal patterns of cAMP-mediated signaling to control basal ganglia circuit functions. In Aim 1, we will determine the spatiotemporal dynamics in real-time of cAMP/PKA during the induction of striatal synaptic depression in specific cell types. In Aim 2, we will monitor the cAMP and PKA temporal signaling profiles in striatal cells in freely moving mice during striatum-dependent behaviors. We will use transgenic mice, genetically encoded biosensors, ex vivo and in vivo optical imaging techniques, and pharmacological tools to address these aims. The experiments in this proposal will combine technically challenging subcellular in vivo measures of neural network dynamics with simultaneous behavioral assessments to determine the causal link between subcellular neuronal transmission and behaviors.