Ionotropic

Ionotropic receptors are a type of ligand-gated ion channels present in the membrane of neurons. They are so named because they respond to the binding of neurotransmitters, which are chemical messengers in the nervous system. When a neurotransmitter binds to an ionotropic receptor, it causes a change in the receptor's shape, which allows ions to flow across the membrane. This flow of ions can either excite or inhibit the neuron, depending on the type of ion and the direction of its flow.

Structure

Ionotropic receptors are composed of multiple protein subunits that come together to form a pore through the membrane. The exact number and arrangement of these subunits can vary, but most ionotropic receptors are thought to have five subunits. Each subunit has a binding site for a neurotransmitter, and when the neurotransmitter binds, it causes a conformational change in the receptor that opens the pore.

Function

The primary function of ionotropic receptors is to quickly transmit signals across the synaptic cleft, which is the small gap between neurons. When a neuron fires, it releases neurotransmitters into the synaptic cleft. These neurotransmitters then bind to ionotropic receptors on the post-synaptic neuron, causing ions to flow across the membrane and either excite or inhibit the neuron.

There are several types of ionotropic receptors, each of which responds to a different neurotransmitter and allows a different type of ion to flow across the membrane. For example, NMDA receptors respond to the neurotransmitter glutamate and allow calcium ions to flow into the neuron, while GABA receptors respond to the neurotransmitter GABA and allow chloride ions to flow into the neuron.

Clinical significance

Ionotropic receptors are involved in many different processes in the body, and abnormalities in these receptors can lead to a variety of health problems. For example, overactivity of NMDA receptors has been implicated in conditions such as schizophrenia and Alzheimer's disease, while underactivity of GABA receptors has been linked to anxiety disorders and epilepsy.

There are many drugs that target ionotropic receptors, either by mimicking the action of neurotransmitters (agonists) or by blocking their action (antagonists). For example, benzodiazepines are a class of drugs that enhance the action of GABA at GABA receptors, and are commonly used to treat anxiety and insomnia.

See also

• Metabotropic receptor
• Neurotransmitter receptor
• Neurotransmission

References

Ionotropic Resources
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