Jm. Dubinsky et Y. Levi, CALCIUM-INDUCED ACTIVATION OF THE MITOCHONDRIAL PERMEABILITY TRANSITION IN HIPPOCAMPAL-NEURONS, Journal of neuroscience research, 53(6), 1998, pp. 728-741
The mitochondrial permeability transition (mPT) has been implicated in
both excitotoxic and apoptotic neuronal cell death, despite the fact
that it has not been previously identified in neurons. To study the mP
T in hippocampal neurons, cultures were loaded with the mitochondrial
dye JC-l and observed with confocal and conventional microscopy, After
pretreatment with 4Br-A23187 and subsequent calcium addition, the ini
tially rodlike mitochondria increased in diameter until mitochondria b
ecame rounded in appearance. Morphological changes reversed when calci
um was removed by EGTA, When neurons were loaded with both fura-2-AM a
nd rhodamine 123, calcium loading produced an increase in cytosolic ca
lcium, mitochondrial depolarization, and similar alterations in mitoch
ondrial morphology, Smaller calcium challenges produced calcium cyclin
g, delaying morphological changes until after secondary depolarization
and calcium release to the cytosol, In neurons exposed to glutamate,
confocal observation of JC-l fluorescence revealed comparable changes
in mitochondrial morphology that were prevented when barium was substi
tuted for calcium, or following pretreatment with the mPT inhibitor, c
yclosporin A. These experiments establish conditions in which the mPT
could be observed in situ in neurons in response to calcium loading. I
n addition, the timing of changes suggested that induction of the perm
eability transition in situ represents a sequence of multiple events t
hat may reflect the multiple open conformations of the mPT pore. (C) 1
998 Wiley-Liss, Inc.