<p>The classical, <strong><a href="http://www.cs.mcgill.ca/~rwest/link-suggestion/wpcd_2008-09_augmented/wp/c/Chemical_synapse.htm" rel="nofollow">chemical synapse</a></strong> offers only one-way traffic. Under physiological conditions, the presynaptic neuron releases vesicles at its axon terminal and the postsynaptic neuron expresses the corresponding receptor proteins in the dendritic region. Conversely, the presynaptic neuron lacks the receptor molecules and the postsynaptic neuron lacks the secretory machinery to release neurotransmitter into the synaptic cleft <a href="http://www.ncbi.nlm.nih.gov/books/NBK11009/" rel="nofollow">(Purves <em>et al</em>., 2001)</a>. </p>

<p>Note, however, that the presynaptic neuron may express regulatory neurotransmitter receptors that bind its own released neurotransmitter, but these do not generate action potentials. And note that the postsynaptic neuron may release neuromodulators in the synaptic cleft. However, these compounds do not initiate action potentials, but have only a regulatory role.</p>

<p>There is, however, also the <strong><a href="http://thebrain.mcgill.ca/flash/d/d_01/d_01_m/d_01_m_ana/d_01_m_ana.html" rel="nofollow">electrical synapse</a></strong>, mediated by gap junctions. These gap junctions are protein pores that electrically and chemically connect adjacent neurons directly. In this case, potential changes generated in one cell may freely spread like a wave to other neighboring cells. Note that this mode of electric coupling does not induce action potentials, but it represents the passive spread of voltage differences, called <strong><a href="http://medical-dictionary.thefreedictionary.com/electrotonic" rel="nofollow">electrotonic coupling</a></strong> <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4019879/" rel="nofollow">(Mylvaganam <em>et al</em>., 2014)</a>. Which cell initiates the wave is irrelevant, as the wave can spread to each cell as long as it is connection via gap junctions. Although these gap junctions are referred to as <em>electrical synapses</em>, the terminology <em>presynaptic</em> and <em>postsynaptic</em> applies in a much looser sense, as any neuron in the tissue can act as either one <a href="http://www.sciencedirect.com/science/article/pii/S0005273604000410" rel="nofollow">(Sheriar, 2004)</a>.  </p>

<p><sub><strong>References</strong><br>
<strong>-</strong> <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4019879/" rel="nofollow">Mylvaganam <em>et al</em>., <em>Front Physiol</em> (2014); <strong>5</strong>: 172</a>
<strong>-</strong> <a href="http://www.ncbi.nlm.nih.gov/books/NBK11009/" rel="nofollow">Purves <em>et al</em>. (eds.), <em>Neuroscience</em>. 2<sup>nd</sup> ed. Sunderland (MA): Sinauer Associates (2001)</a><br>
<strong>-</strong> <a href="http://www.sciencedirect.com/science/article/pii/S0005273604000410" rel="nofollow">Sherair <em>BBA</em> (2004); <strong>1662</strong>(1–2): 113–37</a></sub>  </p>

CC BY-SA 3.0
2016-06-20T19:37:44.480Z
So antidromically moving action potentials in the sense of neural backpropagation (and not electrotonic potentials) can be effected by electrical synapse activity?
huh
CC BY-SA 3.0
2016-06-20T19:54:43.873Z
@huh I'm unsure if antidromic action potentials occur *in vivo*. Gap junctions are, afaik, situated at the soma. .
AliceD
CC BY-SA 3.0
2016-06-20T19:59:44.647Z
Great @Christiaan, thanks for the detail on gap junction location. Am I wrong that there would rather be electrotonic potentials rather than action potentials then?
huh
CC BY-SA 3.0
2016-06-20T20:08:36.577Z
@huh - in fact you are spot on. Thanks for that. I've adapted my answer.
AliceD
CC BY-SA 4.0
2021-05-06T14:13:03.360Z
In the cerebellar cortex there are Golgi cells with dendrodendritic gap junctions, important in the organization of their neural oscillation.
Robin De Schepper
CC BY-SA 3.0
2016-06-20T12:56:33.463Z
2016-06-21T05:33:54.743Z
2016-06-21T05:33:54.743Z
AliceD
<p>Chemical synapses can be bidirectional, especially in invertebrates:</p>

<p><a href="https://www.ncbi.nlm.nih.gov/pubmed/2984356" rel="nofollow noreferrer">https://www.ncbi.nlm.nih.gov/pubmed/2984356</a></p>

<p><a href="https://elifesciences.org/articles/16962" rel="nofollow noreferrer">https://elifesciences.org/articles/16962</a></p>

CC BY-SA 3.0
2018-01-13T20:57:08.877Z
2018-01-13T20:57:08.877Z
invert
<p>Neurons are mostly unidirectional, <em>i.e.</em> electrical impulses enter from one end and leave through the other. Are there bidirectional neurons as well, <em>i.e.</em>, neurons that have a receiving end and a transmitting end that are not mutually exclusive?</p>

<neurophysiology>
Are there bidirectional neurons?
akm
# Are there bidirectional neurons?

(Asked by: username_0 on 2016-06-20)

Neurons are mostly unidirectional, *i.e.* electrical impulses enter from one end and leave through the other. Are there bidirectional neurons as well, *i.e.*, neurons that have a receiving end and a transmitting end that are not mutually exclusive?

**Tags:** neurophysiology


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## 2 answers

### Answer by username_4 on 2018-01-13. Score: 4

Chemical synapses can be bidirectional, especially in username_4ebrates:

<https://www.ncbi.nlm.nih.gov/pubmed/2984356>

<https://elifesciences.org/articles/16962>


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### Answer by username_1 on 2016-06-20. Score: 3

The classical, **[chemical synapse](http://www.cs.mcgill.ca/~rwest/link-suggestion/wpcd_2008-09_augmented/wp/c/Chemical_synapse.htm)** offers only one-way traffic. Under physiological conditions, the presynaptic neuron releases vesicles at its axon terminal and the postsynaptic neuron expresses the corresponding receptor proteins in the dendritic region. Conversely, the presynaptic neuron lacks the receptor molecules and the postsynaptic neuron lacks the secretory machinery to release neurotransmitter into the synaptic cleft [(Purves *et al*., 2001)](http://www.ncbi.nlm.nih.gov/books/NBK11009/).

Note, however, that the presynaptic neuron may express regulatory neurotransmitter receptors that bind its own released neurotransmitter, but these do not generate action potentials. And note that the postsynaptic neuron may release neuromodulators in the synaptic cleft. However, these compounds do not initiate action potentials, but have only a regulatory role.

There is, however, also the **[electrical synapse](http://thebrain.mcgill.ca/flash/d/d_01/d_01_m/d_01_m_ana/d_01_m_ana.html)**, mediated by gap junctions. These gap junctions are protein pores that electrically and chemically connect adjacent neurons directly. In this case, potential changes generated in one cell may freely spread like a wave to other neighboring cells. Note that this mode of electric coupling does not induce action potentials, but it represents the passive spread of voltage differences, called **[electrotonic coupling](http://medical-dictionary.thefreedictionary.com/electrotonic)** [(Mylvaganam *et al*., 2014)](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4019879/). Which cell initiates the wave is irrelevant, as the wave can spread to each cell as long as it is connection via gap junctions. Although these gap junctions are referred to as *electrical synapses*, the terminology *presynaptic* and *postsynaptic* applies in a much looser sense, as any neuron in the tissue can act as either one [(Sheriar, 2004)](http://www.sciencedirect.com/science/article/pii/S0005273604000410).

**References**  
**-** [Mylvaganam *et al*., *Front Physiol* (2014); **5**: 172](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4019879/)
**-** [Purves *et al*. (eds.), *Neuroscience*. 2nd ed. Sunderland (MA): Sinauer Associates (2001)](http://www.ncbi.nlm.nih.gov/books/NBK11009/)  
**-** [Sherair *BBA* (2004); **1662**(1–2): 113–37](http://www.sciencedirect.com/science/article/pii/S0005273604000410)

> **Comments:**
> **username_2**: So antidromically moving action potentials in the sense of neural backpropagation (and not electrotonic potentials) can be effected by electrical synapse activity?  
> **username_1**: @username_2 I'm unsure if antidromic action potentials occur *in vivo*. Gap junctions are, afaik, situated at the soma. .  
> **username_2**: Great @Christiaan, thanks for the detail on gap junction location. Am I wrong that there would rather be electrotonic potentials rather than action potentials then?  
> **username_1**: @username_2 - in fact you are spot on. Thanks for that. I've adapted my answer.  
> **username_3**: In the cerebellar cortex there are Golgi cells with dendrodendritic gap junctions, important in the organization of their neural oscillation.  

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