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Long-lasting inhibitory synaptic depression is age- and calcium-dependent
1Center for Neural Science and Department of Biology, New York University, New York 10003, USA.
Summary
This study reveals that inhibitory synapses in the developing brain undergo activity-dependent weakening, a process crucial for refining neural circuits. This synaptic plasticity, similar to excitatory forms, is calcium-dependent and declines with maturation.
Area of Science:
- Neuroscience
- Developmental Biology
- Synaptic Plasticity
Background:
- Excitatory synapse refinement is activity-dependent, but inhibitory synapse development is less understood.
- The medial nucleus of the trapezoid body (MNTB) to lateral superior olive (LSO) inhibitory projection undergoes developmental synapse elimination.
- Investigating use-dependent changes in inhibitory synaptic strength during development is crucial.
Purpose of the Study:
- To determine if inhibitory synapses exhibit plasticity during development.
- To investigate activity-dependent changes in inhibitory synaptic strength in the MNTB-LSO pathway.
- To characterize the developmental timeline and underlying mechanisms of inhibitory synaptic plasticity.
Main Methods:
- Whole-cell recordings from developing gerbil LSO neurons in brain slices.
- Low-frequency stimulation of MNTB inputs to induce synaptic depression.
- Current-clamp and voltage-clamp recordings to measure inhibitory postsynaptic potentials and currents.
- Manipulating postsynaptic membrane potential (hyperpolarized vs. depolarized states).
Main Results:
- Low-frequency stimulation induced significant depression of inhibitory postsynaptic potentials (IPSPs) and currents.
- Synaptic depression was more pronounced in depolarized LSO neurons (59% vs. 34%).
- This inhibitory plasticity was calcium-dependent and diminished by postnatal days 17-19.
Conclusions:
- Inhibitory synapses undergo activity-dependent depression during a critical developmental period.
- This plasticity may facilitate the elimination and rearrangement of inhibitory synapses.
- Inhibitory synaptic plasticity parallels excitatory forms, suggesting conserved mechanisms in neural circuit refinement.