biostudies-literatureHayward RFNIMH NIH HHSNINDS NIH HHS102983https://www.ebi.ac.uk/biostudies/studies/S-EPMC11735331biostudies-literatureUnknown125Calcium mediates many important signals in dendrites. However, the basic transport properties of calcium in dendrites have been difficult to measure: how far and how fast does a local influx of calcium propagate? We developed an all-optical system for simultaneous targeted Ca²⁺ import and Ca²⁺ concentration mapping. We co-expressed a blue light-activated calcium selective channelrhodopsin, CapChR2, with a far-red calcium sensor, FR-GECO1c, in cultured rat hippocampal neurons, and used patterned optogenetic stimulation to introduce calcium into cells with user-defined patterns of space and time. We determined a mean steady-state length constant for Ca²⁺ transport ϕ ∼ 5.8 μm, a half-life for return to baseline t_1/2 ∼ 1.7 s, and an effective diffusion coefficient D ∼ 20 μm²/s, though there were substantial differences in Ca²⁺ dynamics between proximal and distal dendrites. At high Ca²⁺ concentration, distal dendrites showed nonlinear activation of Ca²⁺ efflux, which we pharmacologically ascribed to the NCX1 antiporter. Genetically encoded tools for all-optical mapping of Ca²⁺ transport and handling provide a powerful capability for studying this important messenger.Cell calciumAll-optical mapping of Ca<sup>2+</sup> transport and homeostasis in dendrites.PMC11735331RF1 MH117042RF1 NS126043Cohen AEHayward RFfalseAll-optical mapping of Ca<sup>2+</sup> transport and homeostasis in dendrites.Calcium mediates many important signals in dendrites. However, the basic transport properties of calcium in dendrites have been difficult to measure: how far and how fast does a local influx of calcium propagate? We developed an all-optical system for simultaneous targeted Ca²⁺ import and Ca²⁺ concentration mapping. We co-expressed a blue light-activated calcium selective channelrhodopsin, CapChR2, with a far-red calcium sensor, FR-GECO1c, in cultured rat hippocampal neurons, and used patterned optogenetic stimulation to introduce calcium into cells with user-defined patterns of space and time. We determined a mean steady-state length constant for Ca²⁺ transport ϕ ∼ 5.8 μm, a half-life for return to baseline t_1/2 ∼ 1.7 s, and an effective diffusion coefficient D ∼ 20 μm²/s, though there were substantial differences in Ca²⁺ dynamics between proximal and distal dendrites. At high Ca²⁺ concentration, distal dendrites showed nonlinear activation of Ca²⁺ efflux, which we pharmacologically ascribed to the NCX1 antiporter. Genetically encoded tools for all-optical mapping of Ca²⁺ transport and handling provide a powerful capability for studying this important messenger.2025-01-01T00:00:00Z2025 Jan2026-06-06T08:44:30.383Z2026-05-28T03:12:10.197ZS-EPMC117353313966213710.1016/j.ceca.2024.102983