acetylcholine

[jaeida8]

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other than the fact that nicotinic acetylcholine receptors are ionotropic and muscarinic acetylcholine receptors are metabotropic, what is the difference between these receptors (in terms of location in the body, etc.)?

 

[BamaFlip]

Hope this is not too lengthy, but you caught me in the middle of neuro, so this stuff is fresh on my mind.

Nicotinic acetylcholine receptors (ionotropic/ligand gated) are found at the neuromuscular junctions. So these would involve motor neurons. Some of these receptors can occur in preganglionic autonomics however (along with Muscaranic receptors......I know, that's tricky stuff).

Muscarinic acetylcholine receptors (metabotropic/G-protein coupled receptors) are found on smooth and cardiac muscle fibers and on many different neurons. For example, acetylcholine, when applied to a muscarinic receptor on cardiac muscle, causes the increase opening of K+ channels and the initiation of a slow IPSP (slowing down the heart).
A few examples of terminals with Muscarinic acetylcholine receptors are:
1. Thalamus (Reticular Formation)
2. Cerebral Cortex and Amygdala (Basal Nucleus)
3. Hippocampus (Septal Nuclei)
4. Local connections such as between the caudate nucleus and the putamen (components that make up the striatum)

 

[neurogeek]

Also, nicotinic and muscarinic receptors are found throughout the CNS. Acetylcholine acts as a very influential neuromodulator in the CNS. I work more with muscarinic receptors, so I can tell you that they play an important role in modulation of long-term potentiation (LTP - thought to be important for memory), network synchronization, neurotransmitter release, and other things.

In the brain ACh is THE main player in the reticular activating system which controls alertness and such. Also there is a large cholinergic input into the hippocampus and parahippocampal region. If you want to look up some papers about nicotinic receptors in the CNS - try looking for papers from John Dani.