Musk, for remembering cholinergic subtypes

Depending on where you went to school and what type of pharmacology class you had, you may or may not have gotten into receptor subtypes for drugs that affect the nervous system.

Of course, you might not find receptor subtypes helpful. I do. Remembering which pressors affect alpha-1, etc receptors helps me remember the therapeutic and non-therapeutic effects of Levophed, Dobutamine, etc.

But I always have a hard time with the cholinergic system. I've been out of school and working for a while now, and every time I try to recall this information, I get it scrambled.

But now I think I have a trick for getting it right!

let's review:

The cholinergic system refers to those parts of the nervous system that use acetylcholine as a neurotransmitter. This pretty much comprises the entire peripheral nervous system except for the stimulation of various organs by adrenaline and noradrenaline.

The differences in the way acetylcholine affects the body have to do with the cholinergic system's different types of neurotransmitter receptors. There three major types. (Actually, the situation is a lot more complicated, but this works for our needs.) They are:

muscarinic receptors (M)
nicotinic-M receptors (NM)
nicotinic-N receptors (NN)

The three types correspond to three major functions of the cholinergic system. They are:

stimulating other nerves
stimulating skeletal muscles
stimulating organs

In the diagram below (original here), adrenaline and noradrenaline are basically the dotted red lines, and the cholinergic system is the solid red and blue lines.
The solid red lines stimulate other nerves, while the solid blue lines stimulate organs. Stimulation of the skeletal muscles isn't shown.

So how do you remember which receptors do what?

Well, one of them is easy. The stimulation of other nerves at neuronal ganglia require NN receptors. N is for "N"erves and "N"eurons.

Likewise, we can remember that "M" is for skeletal "M"uscle. But this is where I always get mixed up because is it the M for muscarinic receptors or the M for nicotinic-M receptors? So I have a new memory trick.

Remember that adreneline is mostly responsible for "fight or flight" symptoms. The odd man out is sweating. Although getting chased by a sabertooth tiger is going to make us sweat, it isn't adreneline that stimulates sweating. Sweating comes from cholinergic stimulation*.

And what does sweating cause? It causes "musky" scents. "Musk" for "muscarinic." Yes, it is the M receptors that are found on organs and sweat glands, and it is the "M" in NM receptors that stands for "M"uscle. NM receptors allow stimulation of skeletal muscle.


* If you can't remember that sweating is cholinergic, you're probably screwed. But if you can, try to remember that during Operation Desert Storm, the army couldn't use atropine because atropine would stop sweating, and the soldiers would overheat in their biochemical warfare suits.