Ionotropic Receptors

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Ionotropic receptors are one of two primary neurotransmitter receptors. Ionotropic receptors are mainly located along the cell body, but they can be found anywhere along a neuron if there is a synapse. Receptors can be located in many different parts of the body and act as excitatory or inhibitor receptors for a specific neurotransmitter, but are ionotropic receptors the same?

An ionotropic receptor is also known as a ligand-gated channel. These receptors respond to ligand binding by opening an ion channel. When the ion channel is open, ions are allowed to flow to the cell, increasing or decreasing the possibility of an action that is fired.

Ionotropic receptors have a vital role to play in the body. They regulate membrane potential, neurotransmitter release, and intercellular communication, among other functions. Dysfunctional ion channels in ionotropic receptors can cause cognitive impairment and lead to neurodegenerative diseases like Alzheimer's. Many of the treatments used for these diseases target ionotropic receptors.

What Is The Definition Of Ionotropic Receptors?

Ionotropic receptors are gated ion channels comprising three, four, or five protein subunits. When they are together, the subunits form an ion-conducting pore in the middle of the receptor. The binding of the ligand (neurotransmitter or hormone) is what causes the opening of the channel and allows ions to flow through it.

The ionotropic receptors can be divided into four categories, each having a different molecular structure. Ionotropic receptors are targets for therapeutic compounds and can also be affected by endogenous substances.

Ionotropic receptors play a vital role in long-term memory and other functions throughout the body. Ionotropic receptors function by opening ion channels that allow specific ions to flow in and out of a cell.

What Is The Ionotropic Effect?

The ionotropic effect can be defined as the effect that a substance or hormone has on activating and deactivating ionotropic receptors. This negative or positive effect is usually used to describe acetylcholine on nicotinic receptors or GABA on GABAa receptors. In addition, this term is used to explain how the heart muscles contract and is also known as the ionotropic effect.

Ionotropic Receptors Vs. Metabotropic Receptors

A receptor is a molecule that binds to a ligand to produce some effect. There are receptors all over the human body. Some of these receptors are enzymes, and others are coupled with enzymes. Many receptors need a second messenger to carry out the response. The ionotropic receptor is one of the most unique receptors that do not require a response.

When considering receptors, there are two types of receptors in the nervous system: ionotropic and metabotropic. Neurotransmitters activate both these receptors. The difference between the two types of receptors is that ionotropic receptors are channel linked, while metabotropic receptors use G-proteins to initiate a series of molecules.

Ionotropic receptors are ion channels that open and close when binding to a chemical messenger like a neurotransmitter. Ionotropic receptors are also called ion channels; these channels work to help transport ions. The binding of these ions to receptors opens the ion channels. Ion channels never remain open or closed all the time. Ionotropic receptors mostly remain closed.

The binding of ions does not activate secondary molecules, making the ionotropic receptors' effect short-lived.

A metabotropic receptor is a receptor found on the surface of cells and is involved in signaling through the secondary messenger binding receptor. The most important part of the metabotropic receptor is the G-protein receptor. Unlike the ionotropic receptors, the metabotropic receptors take longer to open because it involves activating more molecules than the ionotropic receptors.

Metabotropic receptors can close or open a channel and can also participate in neurotransmission.

Both ionotropic and metabotropic receptors play essential roles in regulating the metabolism. Most of the metabolic pathways take place through receptors that bind with ligands.

The Difference Between Ionotropic And Metabotropic Receptors

The most significant difference between the ionotropic and metabotropic receptors is the type of ligand that binds to the receptors. Non-ionic ligands bind to metabotropic receptors, and ionic ligands bind to ionotropic receptors. Ionic ligands like  K+, Na+, Cl–, and Ca2+ bind to ionotropic receptors, while metabotropic receptors only bind with non-ionic ligands like G-proteins and chemical receptors.

When binding occurs, the ionic receptors open a gated channel while the metabotropic receptors initiate a reaction or send a signal. Both metabotropic and ionotropic receptors play essential roles in neurotransmission, but the stability of the effect of the metabotropic receptors is much more widespread.

What Makes Ionotropic And Metabotropic Receptors Similar?

Ionotropic and metabotropic receptors are not the same, but they have a few similarities. These similarities are:

  • Ionotropic and metabotropic receptors play an important role in neurotransmission
  • Both receptors bind to specific ligands
  • Ionotropic and metabotropic receptors are types of membrane receptors
  • Both receptors are very sensitive when binding with ligands

Examples Of Ionotropic Receptors

Some ionotropic receptors are found in sensory airway terminals. These receptors include serotonin, ATP, Nicotinic Acetylcholine, and Gaba Receptors.

Serotonin Receptors

The serotonin receptors are found in the chemoreceptor zone. The binding to serotonin causes the opening of ion channels which initiates depolarization creating an action effect.

ATP Receptors

The ATP receptors are also known as the P2X receptors. These receptors have two transmembrane domains. One of these domains is called the extracellular domain and is a ligand binding domain. The binding of ATP to the extracellular domain opens the ion channel, creating the action potential.

The ATP receptors perform functions that include:

  • Regulating blood vessel tone
  • Regulating heart rate
  • Contracting the bladder for micturition
  • Apoptosis
  • Platelet aggregation

Nicotinic Acetylcholine Receptors

These receptors are in the neuromuscular junction. This receptor allows nerve impulses to pass from the motor neuron to the skeletal muscles.

GABA Receptors

GABA receptors can be found in the CNS and are the primary inhibitory receptors in the brain. These receptors play a vital role in inducing sleep, relieving anxiety, and helping people stay calm.

Both ionotropic and metabotropic receptors play a function in membrane transport. These receptors also signal transduction. While the ionotropic receptors bind to ligands, the metabotropic receptors bind with chemical or G-protein receptors.

The main difference between the ionotropic and the metabotropic receptors is that one works as a channel that opens and closes, and the other does not work as a channel.

Where Are Ionotropic Receptors Found?

Ionotropic receptors are found on dendrites. Ionotropic receptors can also be found anywhere along a neuron if there is a synapse. These receptors can be opened with a specific ligand because neurotransmitters and receptors can only bind and open to particular receptors.

What Are Ionotropic Glutamate Receptors?

The ionotropic glutamate receptors are one of the most common types of receptors found in the brain. Ionotropic glutamate receptors are gated ion channels activated by the neurotransmitter glutamate. These glutamate receptors are responsible for mediating most of the synaptic transmission through the CNS and play an essential role in brain function, particularly in learning and memory.

The glutamate receptors are made up of subunits, and each subunit consists of three domains: the ligand binding domain, the trans member domain, and the amino-terminal domain. There are three groups of glutamate receptors, the AMPA, Kainate, and NMDA, and they have many pharmacology similarities in their structure.

All ionotropic glutamate receptors have the same structure. Like the GABA receptors, the ionotropic glutamate receptor has subunits with hydrophobic regions. What makes these subunits different is the domain has a re-entrant loop which gives the subunits an extracellular and intracellular terminus.

What Makes Ionotropic Glutamate Receptors Diverse?

Ionotropic glutamate receptors are one of the human body's most diverse receptors. Their diversity is displayed before and after gene transcription. After gene transcription, pre-mRNA can be modified; this happens when different regions of this molecule can be put together, creating multiple mRNAs which can be formed into other proteins.

This process is prevalent with neuroreceptors. A site of extensive splice variation is at the C-terminus of the ionotropic glutamate receptors. The C-terminus also has multiple protein interactions, leading to differences in the subunit's localization.

What Are The Functions Of The Ionotropic Glutamate Receptors?

Glutamate is the primary excitatory neurotransmitter in the central nervous system. The ionotropic glutamate receptors also play a part in excitatory synaptic transmission and is the process by which neurons communicate.

An electrical impulse in one of these cells causes calcium ions to release the neurotransmitter glutamate. The neurotransmitter diffuses across cells and stimulates cells in a chain by interacting with proteins.

Are Ionotropic Receptors Excitatory Or Inhibibitory?

Ionotropic receptors can be both excitatory and inhibitory based on their equilibrium potential. When these receptors passions, it impacts the membrane potential. Metabotropic receptors can also have excitatory effects when activated, as well as inhibitory effects.

These effects occur when the metabotropic receptor triggers a signaling pathway, and this pathway opens or closes the ion channel.

Are Ionotropic Receptors Fast Or Slow?

Ionotropic mechanisms lead to opening channels; these receptors are like voltage-gated channels with selectivity filters; the only difference between the and voltage-gated channels is that they have a different gating mechanism. This difference in their gating mechanism causes the opening and closing of the channel.

Most receptors can be identified according to their speed and their action.

In contrast, metabotropic receptors are slow receptors because they alter the function of ion channels, and metabotropic mechanisms can lead to the opening, closing, or modulation of ion channels. A neurotransmitter can act via both ionotropic and metabotropic receptors with the same synapse.

Are Postsynaptic Receptors Ionotropic Or Metabotropic

A postsynaptic receptor is classified as a receptor located on the cell membrane or inside a postsynaptic neuron.

There are two families of postsynaptic receptors; these are ionotropic and metabotropic. Receptor proteins complete the opening or closing of the postsynaptic ion channels. Receptors like ionotropic receptors comprise individual protein subunits that make up an ion channel's pores.

The ionotropic receptors are linked directly to ion channels and contain functional domains, which include an extracellular site that binds neurotransmitters and a membrane domain that forms an ion channel.

The second family of receptors is the metabotropic receptors. These receptors don't have ion channels but use G-proteins which affect channel activation, making metabotropic receptors known as G-protein coupled receptors.

Metabotropic receptors have an extracellular domain containing neurotransmitters and an intracellular domain that binds to the G-proteins. This binding process activates the G-proteins, which disassociate from the receptor and communicates directly with the ion channels to make messengers that either open or close ion channels.

The ionotropic and metabotropic families of postsynaptic receptors produce postsynaptic actions ranging from less than a millisecond to minutes, hours, and days. While the movement created by ionotropic receptors is fast, metabotropic receptors make a much slower response. This slower response is due to the process of many proteins having to bind to elicit a response.

Equilibrium Potential

Ions move through gated channels and try to reach equilibrium. As this process occurs, the neuron's membrane potential comes closer to the ion's equilibrium potential. Using sodium as an example, as the gated channel opens, sodium flows into the membrane until it reaches its equilibrium potential.

Reversal Potential

Reversal Potential is when the ion flow through the receptor is at equilibrium. Therefore, the way the ion flows through the receptor is able to be predicted if the reversal potential is known.

Receptors Selective To One Ion

Ionotropic receptors can be selective. The selective ionotropic receptors are particular to one ion, and only one ion will open. The reversal potential is then the same as the equilibrium potential of the ion. For example, the receptors glycine and GABA only allow chloride ions to cross the membrane; this means the reversal potential of these receptors is equal to the equilibrium potential of chloride.


Ionotropic receptors are gated ion channels that open when binding to a specific neurotransmitter. Ionotropic receptors are along dendrites. These receptors can also occur anywhere on a neuron if a synapse occurs. The ligand-gated ion channels in ionotropic receptors are essential for getting information from neurons.

Reference this article:

Practical Psychology. (2022, September). Ionotropic Receptors. Retrieved from

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