Ionotropic Receptors (Ligand-Gated Channels)
Objective 4: Describe the function of a ligand-gated ion channel.
Some receptors are ligand-gated channels. When the ligand (drug or neurotransmitter) binds to the receptor protein, the protein changes shape and allows the passage of one or more specific ions across the cell membrane.
Ligand-gated channels are also called ionotropic[1] receptors. The term derives from ions, which can pass through its channel, combined with the Greek word τρόπος (trópos), “a turn”, describing the shape change which is initiated by receptor binding.
The naturally occuring neurotransmitter is a receptor ligand, but so are drugs which bind these receptor proteins.
Agonists are drugs which act in the same way as the naturally occuring neurotransmitter. In some cases, agonists bind more strongly to the receptor than even the naturally occuring neurotransmitter.
Antagonists are drugs which partially or completely block the response of the naturally occuring neurotransmitter. In a novel, the antagonist is trying to stop the main character from carrying out an action. It’s the same for receptor antagonists; they get in the way of what the neurotransmitter is trying to do.
- this word is pronounced eye-on-oh-troh-pick, even though it shares a Greek root with tropic, as in tropical regions of Earth. ↵
