The Journal of Neuroscience, August 1, 2000, 20(15):5820-5826
Long-Lasting Inhibitory Synaptic Depression is Age- and
Calcium-Dependent
Vibhakar C.
Kotak1 and
Dan H.
Sanes1, 2
1 Center for Neural Science and
2 Department of Biology, New York University, New
York, New York 10003
The developmental refinement of excitatory synapses is often
influenced by neuronal activity, and underlying synaptic mechanisms have been suggested. In contrast, few studies have asked whether inhibitory synapses are reorganized during development and whether this
is accompanied by use-dependent changes of inhibitory synaptic strength. The topographic inhibitory projection from the medial nucleus
of the trapezoid body (MNTB) to the lateral superior olive (LSO)
undergoes synapse elimination during development (Sanes and
Takács, 1993). To determine whether there is an associated period
of synaptic plasticity, whole-cell recordings were obtained from
developing LSO neurons of gerbils in a brain slice preparation. In
current-clamp recordings, low-frequency stimulation of the MNTB led to
a decline in IPSP amplitude by 43%. In voltage-clamp recordings,
hyperpolarized LSO neurons also exhibited a long-lasting depression of
MNTB-evoked inhibitory synaptic currents (34%) after low-frequency
stimulation. When LSO neurons were depolarized, low-frequency
stimulation of the MNTB produced a significantly larger inhibitory
synaptic depression (59%). This synaptic plasticity declined
dramatically by postnatal days 17-19. Similar to well studied forms of
excitatory synaptic plasticity, inhibitory depression depended on
postsynaptic calcium. We propose that such activity-dependent synaptic
depression may support the developmental rearrangement of inhibitory
terminals as they compete with neighboring excitatory and/or inhibitory inputs.
Key words:
LTD; LSO; inhibition; development; synaptogenesis; calcium
Copyright © 2000 Society for Neuroscience 0270-6474/00/20155820-07$05.00/0