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Bioluminescence imaging of mitochondrial Ca 2 + dynamics in soma and neurites of individual adult mouse sympathetic neurons
Author(s) -
Núñez Lucía,
Senovilla Laura,
SanzBlasco Sara,
Chamero Pablo,
Alonso María T.,
Villalobos Carlos,
GarcíaSancho Javier
Publication year - 2007
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2006.126524
Subject(s) - aequorin , exocytosis , neurite , mitochondrion , endoplasmic reticulum , superior cervical ganglion , microbiology and biotechnology , biophysics , soma , biology , neurotransmitter , ruthenium red , calcium , ionomycin , chemistry , neuroscience , endocrinology , biochemistry , central nervous system , organic chemistry , secretion , in vitro , intracellular
Changes in the cytosolic Ca 2+ concentration ([Ca 2+ ] c ) are essential for triggering neurotransmitter release from presynaptic nerve terminals. Calcium‐induced Ca 2+ release (CICR) from the endoplasmic reticulum (ER) may amplify the [Ca 2+ ] c signals and facilitate neurotransmitter release in sympathetic neurons. In adrenal chromaffin cells, functional triads are formed by voltage‐operated Ca 2+ channels (VOCCs), CICR sites and mitochondria. In fact, mitochondria take up most of the Ca 2+ load entering the cells and are essential for shaping [Ca 2+ ] c signals and exocytosis. Here we have investigated the existence of such functional triads in sympathetic neurons. The mitochondrial Ca 2+ concentration ([Ca 2+ ] m ) in soma and neurites of individual mouse superior cervical ganglion (SCG) neurons was monitored by bioluminescence imaging of targeted aequorins. In soma, Ca 2+ entry through VOCCs evoked rapid, near millimolar [Ca 2+ ] m increases in a subpopulation of mitochondria containing about 40% of the aequorin. Caffeine evoked a similar [Ca 2+ ] m increase in a mitochondrial pool containing about 30% of the aequorin and overlapping with the VOCC‐sensitive pool. These observations suggest the existence of functional triads similar to the ones described in chromaffin cells. In neurites, mitochondria were able to buffer [Ca 2+ ] c increases resulting from activation of VOCCs but not those mediated by caffeine‐induced Ca 2+ release from the ER. The weaker Ca 2+ buffering by mitochondria in neurites could contribute to facilitate Ca 2+ ‐induced exocytosis at the presynaptic sites.