2-Minute Neuroscience: Receptors & Ligands Video Lecture | A-Z Guide to Neuroscience - Personal Learning

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 type are called ionotropic receptors.
Ionotropic receptors have a site where a neurotransmitter
can bind, called the binding site.
When neurotransmitter binds here, it causes
a channel to open in the receptor, and ions
are permitted to flow into the neuron.
This can change the membrane potential of
the neuron, and send a signal, known as the
action potential, down that neuron.
The neurotransmitter that binds is called
the ligand, which is just a term for any substance
that can bind to a target protein.
Thus, ionotropic receptors are also called
ligand-gated ion channels.
The other type of receptors are metabotropic
receptors, also known as G-protein coupled
receptors.
Neurotransmitters also bind to these receptors,
but instead of immediately opening an ion
channel, the next step after binding is the
activation of an intermediate protein called
a G-protein.
The G-protein can then influence the opening
of ion channels, but it can also affect enzymes
and activate intracellular signaling molecules
known as second messengers, which can initiate
signaling cascades within the cell.
G-protein coupled receptors thus tend to have
a 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 and have
a variety of effects.
If they have the same effect as the neurotransmitter,
they are known as agonists.
If they block the effects of the neurotransmitter,
they are known as antagonists.
Some drugs can bind to the site the neurotransmitter
binds to and have the exact opposite effect
of the neurotransmitter.
These are called inverse agonists.
Finally, drugs 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 are called neuromodulators,
and said to have an allosteric effect.