Related Experiment Video
Updated: Jun 1, 2026
07:44
Evaluation of Synapse Density in Hippocampal Rodent Brain Slices
Published on: October 6, 2017
The gray area between synapse structure and function-Gray's synapse types I and II revisited.
Cornelius J H M Klemann1, Eric W Roubos
1Department of Cellular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
Synapse (New York, N.Y.)
|June 10, 2011
Summary
The traditional Gray synapse concept, linking synapse structure to function, is challenged by new evidence. Emerging research suggests synapse function relies more on postsynaptic receptors than presynaptic morphology.
Area of Science:
- Neuroscience
- Cell Biology
- Synaptic Plasticity
Background:
- The Gray synapse concept historically classified synapses as excitatory (Type I, asymmetric) or inhibitory (Type II, symmetric).
- This classification was supported by neurotransmitter localization (glutamate in Type I, GABA in Type II).
- This concept remains influential in neuroscience literature.
Purpose of the Study:
- To re-evaluate the validity of the functional Gray synapse concept.
- To explore alternative interpretations of synaptic morphology and function.
- To investigate the roles of different synapse types beyond simple excitation/inhibition.
Main Methods:
- Review of ultrastructural parameters of synapses.
- Analysis of morphological and functional evidence challenging the Gray synapse concept.
- Consideration of the role of postsynaptic receptors and signal transduction.
Main Results:
- Morphological features (vesicle shape, synaptic cleft, postsynaptic density) do not consistently align with the proposed excitatory/inhibitory functions.
- Synapse function is increasingly understood to depend on postsynaptic receptors and signaling pathways.
- Many synapses exhibit features that make classification difficult, questioning the role of postsynaptic density as solely indicative of excitation.
Conclusions:
- The functional Gray synapse concept requires revision due to accumulated evidence.
- Asymmetric synapses may serve as structural links for long-term neuronal communication.
- Symmetric synapses might mediate transient communication crucial for development, learning, and disease processes.
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