2-Minute Neuroscience: Receptors & Ligands

In my 2-Minute Neuroscience videos I explain neuroscience topics in 2 minutes or less. In this video, I discuss receptors and ligands. I explain the differences between the two main types of neurotransmitter receptors: ionotropic and metabotropic (aka G-protein-coupled) receptors. I also discuss the actions ligands like drugs can have, explaining what agonism, antagonism, inverse agonism, and allosterism (aka neuromodulation) are.

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TRANSCRIPT:

Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss receptors and ligands.

When neurotransmitter molecules are released from a neuron, they pass the signal to the next neuron by interacting with receptors on that neuron. These receptors are made up of proteins embedded in the membrane of the postsynaptic cell.

There are two broad families of neurotransmitter receptors. One family is called ionotropic receptors. Ionotropic receptors have a site where a neurotransmitter can bind, called the binding site. When the neurotransmitter binds to the binding site, it causes a channel to open in the receptor, and ions are permitted to flow into the postsynaptic cell. This can change the membrane potential of the postsynaptic neuron, and send a signal, known as an action potential, down the neuron. The neurotransmitter that binds is called the ligand, which is just a term for any substance that can bind to the target protein. Thus, ionotropic receptors are also called ligand-gated ion channels.

The other family of receptors are metabotropic receptors, also known as G-protein coupled receptors. Neurotransmitters also bind to these receptors, but instead of simply opening an ion channel, the next step is the activation of an intermediate prtein called a G-protein. The G-protein can then influence the opening of ion channels, but they can also affect enzymes and initiate signaling cascades within the cell. G-protein coupled receptors thus tend to have slower action, but can have more widespread effects due to their ability to influence various molecules throughout the cell.

Ligands other than neurotransmitters (such as drugs) can also bind to receptors can have a few different effects. If they have the same effect as the neurotransmitter, they are known as agonists. If they have the opposite effect of the neurotransmitter, or block the effects of the neurotransmitter, they are known as antagonists. They also may bind to a site on the receptor that is separate from the site where the neurotransmitter binds and affect the likelihood that the neurotransmitter will bind. In this case, they have an allosteric or neuromodulatory effect.

REFERENCES:

Kandel ER, Schwartz JH, Jessell TM 2000. Principles of Neural Science, 5th ed. McGraw-Hill, New York.