<p><strong>Short answer</strong><br />
I cannot give a conclusive answer, but if you are talking about a schoolbook neuron with different neurons synapsing onto it, then excitation is indeed generally mediated by another neurotransmitter than inhibition.
<br><br>
<strong>Background</strong></p>
<ul>
<li>First and foremost, in the central nervous system the principal excitatory neurotransmitter is <strong><a href="https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors" rel="nofollow noreferrer">glutamate</a></strong>, and the principal inhibitory neurotransmitter is <strong><a href="https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors" rel="nofollow noreferrer">GABA</a></strong>. However, <strong><a href="https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors" rel="nofollow noreferrer">neurotransmitters in themselves are not excitatory or inhibitory</a></strong>, it is the receptors that govern their workings. In this regard it is important to know that none of the Glu receptors (ionotropic or metabotropic) is inhibitory, at least as faras I am aware, and none of the GABA receptors is excitatory.</li>
<li>Secondly, from a postsynaptic point of view, synapses with different input cells are separate. In other words, a glutamatergic neuron never secretes GABA in the same synapse or <em>vice versa</em>. In effect, neurotransmitter systems are separated. Often, a principal neurotransmitter may be accompanied by <a href="https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors" rel="nofollow noreferrer">neuromodulators</a>, but never will one neuron release opposite effector molecules. Instead, opposing inputs are imposed by separate cells, each with their own neurotransmitter system.</li>
<li>The neurotransmitter <strong><a href="http://www.wikilectures.eu/w/Excitation-contraction_coupling_in_skeletal_muscle" rel="nofollow noreferrer">acetylcholine</a></strong> can be excitatory at the neuromuscular junction in skeletal muscle, causing the muscle to contract. In contrast, it is inhibitory in the heart, where it slows heart rate. So Ach can have dualistic and even opposing actions, but the respective <strong>receptors are different and geographically segregated in different neurons</strong>;</li>
<li>But, this is schoolbook, anthropocentric knowledge, and since you are asking about *any creature (anywhere in the multiverse?), then yeah... I must admit I simply don't know. Little is known about deep sea creatures for instance, and it might as well be that one freaky critter deploys its neurochemicals in totally different and unexpected ways.</li>
</ul>

CC BY-SA 3.0
2017-11-24T03:28:59.263Z
Thanks for the answer and the detail.  I have a feeling that most questions about the nervous system of...anything really...start with "it depends on..." and then takes 50 years of PhD level research to answer...
Michael Stachowsky
CC BY-SA 4.0
2022-08-02T13:53:49.247Z
There certainly are inhibitory presynaptic metabotropic glutamate receptors; they help regulate overexcitability by self-inhibition.
Bryan Krause
CC BY-SA 4.0
2022-08-03T11:40:45.617Z
@BryanKrause that's interesting! Didn't know :)
AliceD
CC BY-SA 4.0
2017-11-23T22:02:21.487Z
2022-08-02T11:23:35.963Z
2022-08-02T11:23:35.963Z
AliceD
<p>If a neuron has both excitatory and inhibitory chemical synapses providing it with input, is it true in all organisms that the chemicals that cause the inhibition are distinct from those that cause the excitation?</p>

<p>Related question:<br>
<a href="https://cogsci.stackexchange.com/questions/18508/what-is-synaptic-polarity-in-a-chemical-synapse">What is &quot;synaptic polarity&quot; in a chemical synapse?</a></p>

CC BY-SA 3.0
2017-11-22T16:52:36.293Z
I don't know enough to answer the "all" aspect, but usually L-glutamate is excitatory and GABA inhibitory.
got trolled too much this week
CC BY-SA 3.0
2017-11-22T16:55:37.373Z
Also, do you count pre-birth and abnormal variations in GABA role? https://www.nature.com/articles/nrn3956
got trolled too much this week
CC BY-SA 3.0
2017-11-22T17:03:04.733Z
@Fizz: I am concerned that perhaps the question is too broad, now that I think of it.  I'm mainly interested in adults who have developed normally
Michael Stachowsky
CC BY-SA 3.0
2017-11-23T13:42:58.040Z
@MichaelStachowsky You can make this question more focused (as you state) by editing it.
Steven Jeuris
<neuroscience><neurophysiology><neuro-transmitters>
Are inhibitory synapses governed by different chemicals than excitatory synapses?
Michael Stachowsky
# Are inhibitory synapses governed by different chemicals than excitatory synapses?

(Asked by: username_0 on 2017-11-22)

If a neuron has both excitatory and inhibitory chemical synapses providing it with input, is it true in all organisms that the chemicals that cause the inhibition are distinct from those that cause the excitation?

Related question:  
[What is "synaptic polarity" in a chemical synapse?](https://cogsci.stackexchange.com/questions/18508/what-is-synaptic-polarity-in-a-chemical-synapse)

**Tags:** neuroscience, neurophysiology, neuro-transmitters

> **Comments:**
> **username_1**: I don't know enough to answer the "all" aspect, but usually L-glutamate is excitatory and GABA inhibitory.  
> **username_1**: Also, do you count pre-birth and abnormal variations in GABA role? https://www.nature.com/articles/nrn3956  
> **username_0**: @Fizz: I am concerned that perhaps the question is too broad, now that I think of it.  I'm mainly interested in adults who have developed normally  
> **username_2**: @MichaelStachowsky You can make this question more focused (as you state) by editing it.  

---

## 1 answers

### Answer by username_3 on 2017-11-23. Score: 3 | Accepted answer

**Short answer**  
I cannot give a conclusive answer, but if you are talking about a schoolbook neuron with different neurons synapsing onto it, then excitation is indeed generally mediated by another neurotransmitter than inhibition.
  
  
**Background**

* First and foremost, in the central nervous system the principal excitatory neurotransmitter is **[glutamate](https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors)**, and the principal inhibitory neurotransmitter is **[GABA](https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors)**. However, **[neurotransmitters in themselves are not excitatory or inhibitory](https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors)**, it is the receptors that govern their workings. In this regard it is important to know that none of the Glu receptors (ionotropic or metabotropic) is inhibitory, at least as faras I am aware, and none of the GABA receptors is excitatory.
* Secondly, from a postsynaptic point of view, synapses with different input cells are separate. In other words, a glutamatergic neuron never secretes GABA in the same synapse or *vice versa*. In effect, neurotransmitter systems are separated. Often, a principal neurotransmitter may be accompanied by [neuromodulators](https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/neurotransmitters-their-receptors), but never will one neuron release opposite effector molecules. Instead, opposing inputs are imposed by separate cells, each with their own neurotransmitter system.
* The neurotransmitter **[acetylcholine](http://www.wikilectures.eu/w/Excitation-contraction_coupling_in_skeletal_muscle)** can be excitatory at the neuromuscular junction in skeletal muscle, causing the muscle to contract. In contrast, it is inhibitory in the heart, where it slows heart rate. So Ach can have dualistic and even opposing actions, but the respective **receptors are different and geographically segregated in different neurons**;
* But, this is schoolbook, anthropocentric knowledge, and since you are asking about \*any creature (anywhere in the multiverse?), then yeah... I must admit I simply don't know. Little is known about deep sea creatures for instance, and it might as well be that one freaky critter deploys its neurochemicals in totally different and unexpected ways.

> **Comments:**
> **username_0**: Thanks for the answer and the detail.  I have a feeling that most questions about the nervous system of...anything really...start with "it depends on..." and then takes 50 years of PhD level research to answer...  
> **username_4**: There certainly are inhibitory presynaptic metabotropic glutamate receptors; they help regulate overexcitability by self-inhibition.  
> **username_3**: @BryanKrause that's interesting! Didn't know :)  

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