synaptic transmission, glycinergic

Definition

Target type: biologicalprocess

The vesicular release of glycine from a presynapse, across a chemical synapse, the subsequent activation of glycine receptors at the postsynapse of a target cell (neuron, muscle, or secretory cell) and the effects of this activation on the postsynaptic membrane potential and ionic composition of the postsynaptic cytosol. This process encompasses both spontaneous and evoked release of neurotransmitter and all parts of synaptic vesicle exocytosis. Evoked transmission starts with the arrival of an action potential at the presynapse. [GOC:dos]

Glycinergic synaptic transmission is a crucial process in the nervous system, mediating fast inhibitory neurotransmission. It involves the release of the neurotransmitter glycine from presynaptic neurons and its binding to glycine receptors on postsynaptic neurons. The process unfolds as follows:

1. **Action Potential Arrival:** An action potential, a nerve impulse, arrives at the presynaptic terminal of a glycinergic neuron.

2. **Calcium Influx:** The action potential depolarizes the presynaptic terminal, opening voltage-gated calcium channels. Calcium ions (Ca2+) rush into the terminal, triggering the release of glycine.

3. **Glycine Release:** Glycine-containing vesicles, small membrane-bound sacs filled with glycine, fuse with the presynaptic membrane and release their contents into the synaptic cleft, the narrow gap between the presynaptic and postsynaptic neurons.

4. **Glycine Binding:** Glycine molecules diffuse across the synaptic cleft and bind to glycine receptors located on the postsynaptic membrane.

5. **Postsynaptic Inhibition:** Glycine receptors are ligand-gated ion channels. When glycine binds, the receptors open, allowing chloride ions (Cl-) to flow into the postsynaptic neuron. This influx of negatively charged chloride ions hyperpolarizes the postsynaptic neuron, making it less likely to fire an action potential. This inhibitory effect reduces neuronal excitability and helps regulate neuronal activity.

6. **Glycine Removal:** To maintain the efficiency of synaptic transmission, glycine is quickly removed from the synaptic cleft by specialized transporter proteins located on presynaptic terminals and glial cells. This removal process ensures that the inhibitory signal is brief and prevents persistent activation of glycine receptors.

Glycinergic synapses play critical roles in various physiological functions, including:

- **Motor Control:** Inhibiting unwanted muscle contractions.
- **Sensory Processing:** Modulating sensory input.
- **Cognitive Functions:** Regulating neuronal activity in the brain.
- **Pain Perception:** Inhibiting pain signals.

Dysregulation of glycinergic transmission has been implicated in various neurological disorders, including:

- **Spinal Cord Injuries:** Loss of glycinergic inhibition can lead to spasticity.
- **Epilepsy:** Reduced glycinergic inhibition may contribute to seizures.
- **Schizophrenia:** Abnormalities in glycine receptors have been associated with cognitive deficits.
- **Autism Spectrum Disorders:** Disrupted glycinergic signaling may play a role in social and communication challenges.'
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Proteins (4)

Compounds (28)