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Neuroreceptor Distribution


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Most people are here are probably familiar with neurotransmitters and receptors. Monoamines, glutamate, hormones, etc act as inhibitors or enhancers in neuronal AP firing processes in the synaptic pathways of the brain.

 

I have some questions about the distribution of neuroreceptors. Is it true that the dendrites of neurons have a wide variation in which receptors they possess? If so is this the mechanism that allows neurotransmitters to target specific of parts of the brain and specific synaptic connections. Is it accurate to say that any given synaptic connection is uniquely coded with a "receptor signature"?

 

Thanks in advance.

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There probably is variety, although the majority would be for a specific type of neurotransmitter. This is best illstrusted by how psychoactive drugs only affect certain parts of the nervous system. Serotonin is used more in the brain, so its logical to conclude neurons in the brain have more serotonin receptors. Same for AChe in the PNS; having a higher concentration of the most needed receptors is more efficient.

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Originally posted by Radical Edward

typically the synapse only deals with one sort of neurotransmitter, this is pretty expected since the actual impulse itself is binary. there are exceptions I believe, but these are pretty rare.

 

I don't think so. The impulse is called an action potential and while it is binary (on/off) it is triggered by an analog mechanism composed of receptors for inhibitors and enhancers. There should in principle, be an array of receptors on dendrites that reflect there function. Having dendrites that respond to only one neurotransmitter would severly reduce brain plasticity and neurological functions and I don't see any reason why evolution should produce such a constrained architecture.

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Originally posted by fafalone

"Specialization"

 

Furthermore, transduction of the action potential down the axon is not related to the type of neurotransmitter used. It's not the neurotransmitters thats moving down it, its just the signal.

 

I appreciate that however the neurochemical makeup of the synapse is key factor in whether a post synaptic neuron will fire or not.

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Originally posted by Radical Edward

 

I think so actually, I did a course on this.

 

Great, then you should be able to explain it to me. If dendites have only one type of neurotransmitter then how can GABA and Glutamate receptors work together to produce inhibition and enhancing effects on the AP? How can cortisol play it's global role?

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Originally posted by Deslaar

 

I appreciate that however the neurochemical makeup of the synapse is key factor in whether a post synaptic neuron will fire or not.

 

 

Um, do you know the difference between an axon and a synapse? Doesn't seem like it.

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Originally posted by fafalone

 

 

Um, do you know the difference between an axon and a synapse? Doesn't seem like it.

 

Sure do. Axon->Synapse->Dendrite. Axon releases neuro transmitters into synapse, dendrite recieves neurotransmitters through receptors, receptors release calcium etc into cell body that affects its AP.

 

Am I being unclear?

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Originally posted by fafalone

My cell molec bio book says any particular nerve cell releases only one type of neurotransmitter; so why would it have receptors for more?

 

Because a neuron connects to more than one other neuron. However, if you molec bio book says that a particular nerve releases only one neurotransmitter then I confused. How old is it?

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Originally posted by fafalone

Furthermore, GABA can have both effects because of how the nerve cell responds to it, not by having different receptors.

 

And what is the mechanism that makes the distinction?

 

BTW just checked Ledoux's book The Synaptic Self, and he states that dendrites can release more than one neurotransmitter.

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Originally posted by fafalone

Published in 2002. Furthermore, I just took a class on it last semester. You are mistaken. Nerve cells specialize to one neurotransmitter.

 

Interesting. I might have to some more research on this. Thanks.

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Originally posted by fafalone

What's the mechanism that makes it a nerve cell? That's just how it specializes.

 

You said that GABA can have a enhancing or inhibitory effect on the AP. What is the mechanism that "decides" which effect to have?

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Originally posted by Deslaar

 

Interesting. I might have to some more research on this. Thanks.

 

I contacted a PhD in Neuroscience at Washington University, your book is outdated. The claim that a neuron produces one neurotransmitter is false, it has been established that "colocalization" is present in neurons. I suspect that this will be shown to be a limiting case of more diverse neurotransmitter distribution.

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Please provide research indicating this is wrong. You can't just claim you contacted someone and provide no reference.

And what was the exact message, because there's bound to be some exceptions and colocalization isn't present in all cells.

 

So either the professor you contacted was wrong, or you just misinterpreted what he said. Either way, you're wrong.

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Originally posted by fafalone

Please provide research indicating this is wrong. You can't just claim you contacted someone and provide no reference.

And what was the exact message, because there's bound to be some exceptions and colocalization isn't present in all cells.

 

So either the professor you contacted was wrong, or you just misinterpreted what he said. Either way, you're wrong.

 

 

ARE YOU CALLING ME A LIAR!!!!!

 

:D just kidding

 

There is very little on the web pertaining to colocalisation. It seems that the subject of neuroreceptor distribution is on the frontier of neuroscience. However you can do a search here:

 

http://www.ncbi.nlm.nih.gov/PubMed/

 

The relevant part of the email is as follows:

 

His source was likely very old. The idea that a neuron contains only one neurotransmitter is outdated...the was known as "Dale's Law" and has been disproven. A neuron CAN contain more than one neurotransmitter, in most cases a neuropeptide and a more "traditional" neurotransmitter. This property is called colocalization.

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Originally posted by fafalone

Just because some cells can produce more than one neurotransmitter doesn't mean most of them do...

 

and a neuropeptide isn't the same thing as a neurotransmitter.

 

Are you upset that you were wrong?

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Originally posted by Deslaar

 

Great, then you should be able to explain it to me. If dendites have only one type of neurotransmitter then how can GABA and Glutamate receptors work together to produce inhibition and enhancing effects on the AP? How can cortisol play it's global role?

 

that's post synaptic, and I would be interested to know how a binary AP would be translated into the release of different neurotransmitters. dunno about cortisol though.

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