Schaffer collateral - CA1 synapse

Definition

Target type: cellularcomponent

A synapse between the Schaffer collateral axon of a CA3 pyramidal cell and a CA1 pyramidal cell. [PMID:16399689]

The Schaffer collateral - CA1 synapse is a prominent excitatory synapse in the hippocampus, playing a crucial role in learning and memory. It involves axons from CA3 pyramidal neurons, known as Schaffer collaterals, forming synapses onto dendrites of CA1 pyramidal neurons. This synapse is characterized by a complex structure and precise molecular machinery involved in signal transmission.

**Presynaptic Components:**

* **Axon terminal:** The presynaptic component of the Schaffer collateral - CA1 synapse is the axon terminal of a CA3 pyramidal neuron. This terminal contains numerous synaptic vesicles filled with the neurotransmitter glutamate.
* **Active zones:** Specialized regions within the presynaptic terminal where neurotransmitter release occurs. These zones are characterized by a dense concentration of proteins involved in vesicle docking, priming, and fusion.

**Postsynaptic Components:**

* **Dendritic spine:** The postsynaptic component is a small, mushroom-shaped protrusion from the dendrite of a CA1 pyramidal neuron. These spines serve as specialized compartments for receiving and integrating synaptic inputs.
* **Postsynaptic density (PSD):** A dense protein scaffold located on the postsynaptic membrane of the dendritic spine. The PSD contains numerous receptors, signaling molecules, and scaffolding proteins that regulate synaptic transmission and plasticity.

**Synaptic Transmission:**

1. **Action potential arrival:** An action potential arriving at the axon terminal of the Schaffer collateral triggers the opening of voltage-gated calcium channels.
2. **Calcium influx:** Calcium ions enter the presynaptic terminal, triggering a cascade of events leading to the fusion of synaptic vesicles with the presynaptic membrane.
3. **Glutamate release:** The fusion of vesicles releases glutamate, the neurotransmitter responsible for excitatory signaling at this synapse, into the synaptic cleft.
4. **Glutamate binding:** Glutamate diffuses across the synaptic cleft and binds to glutamate receptors on the postsynaptic membrane of the dendritic spine.
5. **Postsynaptic signaling:** Glutamate binding to receptors, particularly AMPA and NMDA receptors, initiates a cascade of signaling events that lead to depolarization of the postsynaptic neuron.

**Molecular Machinery:**

* **Glutamate receptors:** AMPA receptors mediate fast excitatory transmission, while NMDA receptors contribute to long-term potentiation (LTP).
* **Scaffolding proteins:** Proteins like PSD-95 and Shank organize the PSD and regulate the function of glutamate receptors.
* **Signaling molecules:** Proteins like CaMKII and PKA are involved in signaling pathways that contribute to synaptic plasticity.

**Synaptic Plasticity:**

* **Long-term potentiation (LTP):** A long-lasting enhancement of synaptic strength that is crucial for learning and memory. LTP at the Schaffer collateral - CA1 synapse is a prominent example of Hebbian plasticity, where strengthening of synapses occurs when pre- and postsynaptic neurons are active simultaneously.
* **Long-term depression (LTD):** A long-lasting weakening of synaptic strength that is also involved in learning and memory. LTD at this synapse is triggered by prolonged low-frequency stimulation.

**Clinical Significance:**

* **Learning and memory:** Disruptions in the Schaffer collateral - CA1 synapse are associated with cognitive impairments, including Alzheimer's disease and other forms of dementia.
* **Epilepsy:** Abnormalities in this synapse have been implicated in the development of epilepsy, suggesting a role in the propagation of seizures.
* **Psychiatric disorders:** The hippocampus and its synapses, including the Schaffer collateral - CA1 synapse, have been implicated in several psychiatric disorders, such as schizophrenia and depression.'
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Proteins (37)

Compounds (1,168)