No abstract

Neuropeptides are abundant signaling molecules in the central nervous system. Yet remarkably little is known about their spatiotemporal spread and biological activity. Here, we developed an integrated optical approach using Plasmonic nAnovesicles and cellbased neurotransmitter fluorescent engineered reporter (CNiFER), or PACE, to probe neuropeptide signaling in the mouse neocortex. Small volumes (fL to pL) of exogenously supplied somatostatin-14 (SST) can be rapidly released under near-infrared light stimulation from nanovesicles implanted in the brain and detected by SST2 CNiFERs with nM sensitivity. Our measurements reveal reduced but synchronized SST transmission within 130 μm, and markedly smaller and delayed transmission at longer distances. These measurements enabled a quantitative estimation of the SST loss rate due to peptide degradation and binding. PACE offers a new tool for determining the spatiotemporal scales of neuropeptide volume transmission and signaling in the brain.

Precise modulation of neuronal activity by neuroactive molecules is essential for understanding brain circuits and behavior. However, tools for highly controllable molecular release are lacking.Here, we developed a photoswitchable nanovesicle with azobenzene-containing phosphatidylcholine (azo-PC), coined 'azosome', for neuromodulation. Irradiation with 365 nm light triggers the trans-to-cis isomerization of azo-PC, resulting in a disordered lipid bilayer with decreased thickness and cargo release. Irradiation with 455 nm light induces reverse isomerization and switches the release off. Real-time fluorescence imaging shows controllable and repeatable cargo release within seconds (< 3 s). Importantly, we demonstrate that SKF-81297, a dopamine D1-receptor agonist, can be released from the azosome to activate cultures of primary striatal neurons. Azosome shows promise in precise optical control over the molecular release and can be a valuable tool for molecular neuroscience studies.

Neuropeptides are essential signaling molecules in the nervous system involved in modulating neural circuits and behavior. Although hypothesized to signal via volume transmission through G-protein coupled receptors (GPCR), remarkably little is known about their extrasynaptic diffusion. Here, we developed an all-optical approach to probe neuropeptide volume transmission in mouse neocortex. To control neuropeptide release, we engineered photosensitive nanovesicles with somatostatin-14 (SST) that is released with near-infrared light stimulation. To detect SST, we created a new cell-based neurotransmitter fluorescent engineered reporter (CNiFER) using the SST2 GPCR. Under two-photon imaging, we determined the time to activate SST2R at defined distances as well as the maximal distance and loss rate for SST volume transmission in neocortex. Importantly, we determined that SST transmission is significantly faster in neocortex with a chemically degraded extracellular matrix, a diseased condition indicated in neuroinflammation and Parkinson′s disease. These new neurotechnologies can reveal important biological signaling processes previously not possible, and provide new opportunities to investigate volume transmission in the brain.

Neuropeptides are abundant signaling molecules in the central nervous system. Yet remarkably little is known about their spatiotemporal spread and biological activity. Here, we developed an integrated optical approach using Plasmonic nAnovesicles and cellbased neurotransmitter fluorescent engineered reporter (CNiFER), or PACE, to probe neuropeptide signaling in the mouse neocortex. Small volumes (fL to pL) of exogenously supplied somatostatin-14 (SST) can be rapidly released under near-infrared light stimulation from nanovesicles implanted in the brain and detected by SST2 CNiFERs with nM sensitivity. Our measurements reveal reduced but synchronized SST transmission within 130 μm, and markedly smaller and delayed transmission at longer distances. These measurements enabled a quantitative estimation of the SST loss rate due to peptide degradation and binding. PACE offers a new tool for determining the spatiotemporal scales of neuropeptide volume transmission and signaling in the brain.