Nicotinic vs. Muscarinic Receptors

[Thoroughbred_Med]

Hey guys,

I have been searching the literature left and right for a clear explanation of where muscarinic cholinergic receptors are located. Mainly, I think I am just tripped up by TBR's question:

"What type of protein receptor is found on the cell membrane of a postganglionic neuron?

A) Nicotinic
B) Muscarinic
C) Alpha adrenergic
D) Beta adrenergic

The answer they have is A. and do not provide an answer explanation. I thought muscarinic cholinergic receptors were located at postganglionic parasympathetic neuron targets... not nicotinic.

Can someone help clear this up for me?

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[victorias]

B, C and D are all GPCR's

Nicotinic receptors are ligand gated ion channels - these are found on postsynaptic neurons since neurotransmitters bind to these receptors, causing ions to flow through.

Also, I think B is wrong because the question is asking for receptors located ON the cell membrane. Muscarinic receptors are embedded within the membrane (7 loops of the GPCR's).

 

[Thoroughbred_Med]

B, C and D are all GPCR's

Nicotinic receptors are ligand gated ion channels - these are found on postsynaptic neurons since neurotransmitters bind to these receptors, causing ions to flow through.

Also, I think B is wrong because the question is asking for receptors located ON the cell membrane. Muscarinic receptors are embedded within the membrane (7 loops of the GPCR's).

hmm the nicotinic cholinergic receptor has transmembrane subunits too...

I just think this is a bad free-standing question. Thank you for pointing out that the adrenergic receptors are G-protiens too though! I totally forgot that

 

[neurodoc]

Hey guys,

I have been searching the literature left and right for a clear explanation of where muscarinic cholinergic receptors are located. Mainly, I think I am just tripped up by TBR's question:

"What type of protein receptor is found on the cell membrane of a postganglionic neuron?

A) Nicotinic
B) Muscarinic
C) Alpha adrenergic
D) Beta adrenergic

The answer they have is A. and do not provide an answer explanation. I thought muscarinic cholinergic receptors were located at postganglionic parasympathetic neuron targets... not nicotinic.

Can someone help clear this up for me?

The post-gangionic cholinergic receptors of neurons of both the sympathetic and parasympathetic systems are nicotinic, so A is the correct answer. You are correct in saying that the postgangionic parasympathetic nerve target organs have muscarinic receptors. The postgangionic sympathetic output involves NE for tissues with adrenergic receptors, though the sweat glands are an exception and are muscarinic.

 

[Thoroughbred_Med]

The post-gangionic cholinergic receptors of neurons of both the sympathetic and parasympathetic systems are nicotinic, so A is the correct answer. You are correct in saying that the postgangionic parasympathetic nerve target organs have muscarinic receptors. The postgangionic sympathetic output involves NE for tissues with adrenergic receptors, though the sweat glands are an exception and are muscarinic.

There are sympathetic post ganglionic cholinergic receptors? I thought they were strictly adrenergic?


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[neurodoc]

There are sympathetic post ganglionic cholinergic receptors? I thought they were strictly adrenergic?


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Just in the sweat glands.

 

[Thoroughbred_Med]

Just in the sweat glands.

And they are nicotinic?


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[neurodoc]

And they are nicotinic?


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No. They are muscarinic.

 

[desperadoflakes]

There are sympathetic post ganglionic cholinergic receptors? I thought they were strictly adrenergic?


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Old thread, but wanted to make it clear.

In both SNS and ParaSNS, you have pre-ganglionic neuron --> post-ganglionic neuron --> target organ

In both, the pre-ganglionic neuron secretes acetylcholine, which binds to nicotinic receptors on the post-ganglionic neuron.

The post-ganglionic neurons of the ParaSNS secrete acetylcholine, which binds to muscarinic receptors on their effector organs.

The post-ganglionic neurons of the SNS secrete norepinephrine or epinephrine, which bind to alpha or beta adrenergic receptors on their effector organs.

A couple exceptions in the SNS:

The adrenal medulla itself can actually be thought of a post-ganglionic neuron. It is activated by a pre-ganglionic neuron that secretes acetylcholine (nicotinic), and it releases epinephrine into the bloodstream.

The sweat glands are enervated by an SNS post-ganglionic neuron that secretes acetylcholine, and they have muscarinic receptors.

 

[Thoroughbred_Med]

Old thread, but wanted to make it clear.

In both SNS and ParaSNS, you have pre-ganglionic neuron --> post-ganglionic neuron --> target organ

In both, the pre-ganglionic neuron secretes acetylcholine, which binds to nicotinic receptors on the post-ganglionic neuron.

The post-ganglionic neurons of the ParaSNS secrete acetylcholine, which binds to muscarinic receptors on their effector organs.

The post-ganglionic neurons of the SNS secrete norepinephrine or epinephrine, which bind to alpha or beta adrenergic receptors on their effector organs.

A couple exceptions in the SNS:

The adrenal medulla itself can actually be thought of a post-ganglionic neuron. It is activated by a pre-ganglionic neuron that secretes acetylcholine (nicotinic), and it releases epinephrine into the bloodstream.

The sweat glands are enervated by an SNS post-ganglionic neuron that secretes acetylcholine, and they have muscarinic receptors.

teehee, this is my old thread.

You're explanation was the best one! Thank you!