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Mapping miniature synaptic currents to single synapses using calcium imaging reveals heterogeneity in postsynaptic
T H Murphy1, J M Baraban, W G Wier
1Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Neuron
|July 1, 1995
Summary
Synaptic transmission variability at individual mammalian central neuron synapses impacts postsynaptic calcium transients. This finding suggests single synapses can modulate intracellular signaling pathways via variable output.
Area of Science:
- Neuroscience
- Cellular Biology
- Synaptic Plasticity
Background:
- Miniature excitatory synaptic currents (MESCs) in mammalian central neurons exhibit significant variability.
- The origin of this variability (within-synapse vs. between-synapse heterogeneity) and its impact on postsynaptic calcium dynamics remain unclear.
Purpose of the Study:
- To investigate whether variability in MESC amplitude and kinetics occurs at individual synapses.
- To determine how synaptic current variability influences associated postsynaptic calcium transients (MSCTs).
Main Methods:
- Simultaneous calcium imaging and patch-clamp recordings were performed on cultured cortical neurons.
- Individual MESCs were mapped to identified synapses exhibiting coincident dendritic MSCTs.
- MSCTs were measured at dendritic sites with multiple synaptic events.
Main Results:
- MSCT amplitude showed considerable variation at individual dendritic sites, even with multiple events.
- Variability in coincident synaptic currents was found to contribute to differences in postsynaptic calcium transient amplitude.
- A direct correlation was established between MESC variability and MSCT amplitude fluctuations.
Conclusions:
- Single synapses possess the intrinsic capacity for variable output, challenging the notion of uniform synaptic transmission.
- Synaptic current variability at the individual synapse level is a key factor influencing postsynaptic calcium signaling.
- Variable synaptic output may allow individual synapses to differentially engage intracellular signaling pathways based on calcium levels.