Biology Reference
In-Depth Information
Ca
2
þ
on synaptic facilitation, the dependence of release kinetics on the time-course
of local [Ca
2
þ
]
i
changes, heterogeneity of vesicle Ca
2
þ
-sensitivity and release
kinetics, the role of Ca
2
þ
in mobilizing vesicles to replenished pools depleted in
synaptic depression, and to compare secretion evoked by global [Ca
2
þ
]
i
manipula-
tion in uncaging to local [Ca
2
þ
]
i
influx though voltage-dependent channels to
address the question of distance of the secretory target from Ca
2
þ
channels and
its changes in development. Kinetic studies of the Ca
2
þ
-dependence of secretion
using DM-nitrophen have also been conduced on cochlear hair cells (
Beutner et al.,
2001
) and photoreceptors (
Duncan et al., 2010
).
Zoran et al. (1991)
used Ca
2
þ
photorelease to study synapse maturation. Spike-
evoked transmitter release begins only several hours after cultured snail neurons
contact a postsynaptic target. DM-nitrophen photolysis showed this developmen-
tal change to result from the delayed increase in Ca
2
þ
-sensitivity of the secretory
machinery.
Long-term potentiation and depression (LTP and LTD) in mammalian cortical
synapses are involved in cognitive processes such as memory consolidation and
spatial learning. We found that a brief but strong postsynaptic [Ca
2
þ
]
i
elevation
was su
cient to induce LTP in rat hippocampal CA1 synapses onto the injected
neuron, while a more prolonged but modest [Ca
2
þ
]
i
elevation specifically induced
LTD, and a brief but modest Ca
2
þ
rise could elicit either (
Malenka et al., 1988;
Neveu and Zucker, 1996a,b; Yang et al., 1999
). By terminating the [Ca
2
þ
]
i
rise
following a brief a
Y
erent tetanus by photoactivating the Ca
2
þ
chelator diazo-4, we
showed that postsynaptic [Ca
2
þ
]
i
must remain elevated for several seconds before it
can induce (
Malenka et al., 1992
). We also found that long-lasting changes in
synaptic transmission at CA3 hippocampal pyramidal cells can be produced by
postsynaptic [Ca
2
þ
]
i
elevations induced by DM-nitrophen, NP-EGTA, or
DMNPE-4 photolysis (
Wang et al., 2004
).
Adi
V
V
erent form of LTD in cerebellar Purkinje neurons that plays a role in
motor skill learning, parallel fiber synapses are depressed when their activity
coincides with postsynaptic firing, especially when the latter is triggered by climb-
ing fiber input.
Lev-Ram et al. (1997)
showed that photolytic release of caged Ca
2
þ
from nitr-7 could replace postsynaptic spiking and that photolytic release of either
caged NO or caged cGMP could replace parallel fiber activity; simultaneous
uncaging of Ca
2
þ
and either NO or cGMP could induce LTD without any
electrical stimulation at all.
Kasono and Hirano (1994)
showed that a modest
release of Ca
2
þ
from nitr-5 depressed responses to glutamate application to a
dendrite only when the stimuli were temporally paired. Using DMNPE-4,
Tanaka et al.
ciently high and prolonged Ca
2
þ
elevation
alone could induce LTD, and that the threshold for LTD induction was history-
dependent.
Depolarization-induced suppression of inhibition (DSI) is another form of
cortical synaptic plasticity, which is mediated by activation of postsynaptic endo-
cannabinoid synthesis by activity-induced [Ca
2
þ
]
i
elevation and subsequent retro-
grade regulation of inhibitory transmitter release. We found identical DSI
(2007)
found that a su
Y
