Peripheral hot spots for local Ca2+ release after single action potentials in sympathetic ganglion neurons.
Ca2+ release from the endoplasmic reticulum (ER) contributes to Ca2+ transients in frog sympathetic ganglion neurons. Here we use video-rate confocal fluo-4 fluorescence imaging to show that single action potentials reproducibly trigger rapidly rising Ca2+ transients at 1-3 local hot spots within the peripheral ER-rich layer in intact neurons in fresh ganglia and in the majority (74%) of cultured neurons. Hot spots were located near the nucleus or the axon hillock region. Other regions exhibited either slower and smaller signals or no response. Ca2+ signals spread into the cell at constant velocity across the ER in nonnuclear regions, indicating active propagation, but spread with a (time)1/2 dependence within the nucleus, consistent with diffusion. 26% of cultured cells exhibited uniform Ca2+ signals around the periphery, but hot spots were produced by loading the cytosol with EGTA or by bathing such cells in low-Ca2+ Ringer's solution. Peripheral hot spots for Ca2+ release within the perinuclear and axon hillock regions provide a mechanism for preferential initiation of nuclear and axonal Ca2+ signals by single action potentials in sympathetic ganglion neurons.
Cseresnyés
Zoltán
Z
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
Schneider
Martin F
MF
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D005728:Ganglia, Sympathetic / Q000502:physiology*; D009474:Neurons / Q000166:cytology* / Q000502:physiology*; D011894:Rana pipiens; D014018:Tissue Distribution
D002118:Calcium