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This is a rudimentary question--perhaps the answer is well known to biologists, but is every neurotransmitter receptor also an ion channel?

For example, NMDAR is a glutamate receptor and cation channel and GABA_A receptors are gated ion channels. Is this true generally? If not, is there a classification of neurotransmitter receptors according to abstract function (e.g. all gated ion channels would form one class, then perhaps there are others)?

Thank you in advance! I am a mathematician just getting interested in some biology problems and trying to organize the basic knowledge in this area. I appreciate any insights here!

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is every neurotransmitter receptor also an ion channel?

No.

There are two general types of receptors for neurotransmitters, ligand gated ion channels and receptors that activate second messenger systems, for example, G protein coupled receptors. They are sometimes referred to as ionotropic and metabotropic receptors. This figure from Principles of Neural Science, Ch. 10 illustrates the difference nicely:

enter image description here

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  • $\begingroup$ Very clear! It's interesting that although not every neurotransmitter receptor is an ion-channel, every receptor does control an ion channel. Perhaps this is too broad a question for a comment, but do metabotropic receptors have any other effects on neuronal signaling apart from affecting the post-synaptic cell's membrane potential through control of ion channels? In other words, is the control of ion channels all that really matters for neuronal signaling via neurotransmitters? $\endgroup$ – wanderingmathematician Aug 9 '18 at 15:15
  • $\begingroup$ @user334137 good question. It turns out, sgnaling at the synapse is as complex and varied as signaling in any cell. Both types of receptors can result in many downstream effects beyond immediate changes in permeability to specific ions. The main difference is in the control of the time course of the response. $\endgroup$ – De Novo Aug 9 '18 at 18:47

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