Ca2+ syntillas, miniature Ca2+ release events in terminals of hypothalamic neurons, are increased in frequency by depolarization in the absence of Ca2+ influx.
Localized, brief Ca2+ transients (Ca2+ syntillas) caused by release from intracellular stores were found in isolated nerve terminals from magnocellular hypothalamic neurons and examined quantitatively using a signal mass approach to Ca2+ imaging. Ca2+ syntillas (scintilla, L., spark, from a synaptic structure, a nerve terminal) are caused by release of approximately 250,000 Ca ions on average by a Ca2+ flux lasting on the order of tens of milliseconds and occur spontaneously at a membrane potential of -80 mV. Syntillas are unaffected by removal of extracellular Ca2+, are mediated by ryanodine receptors (RyRs) and are increased in frequency, in the absence of extracellular Ca2+, by physiological levels of depolarization. This represents the first direct demonstration of mobilization of Ca2+ from intracellular stores in neurons by depolarization without Ca2+ influx. The regulation of syntillas by depolarization provides a new link between neuronal activity and cytosolic [Ca2+] in nerve terminals.
De Crescenzo
Valérie
V
Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
ZhuGe
Ronghua
R
Velázquez-Marrero
Cristina
C
Lifshitz
Lawrence M
LM
Custer
Edward
E
Carmichael
Jeffrey
J
Lai
F Anthony
FA
Tuft
Richard A
RA
Fogarty
Kevin E
KE
Lemos
José R
JR
Walsh
John V
JV
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D007031:Hypothalamus / Q000737:chemistry / Q000166:cytology*; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism
D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium