Posted by fachad on March 23, 2002, at 11:03:20
In reply to Fachad, others: question about TCA's and receptors, posted by Janelle on March 23, 2002, at 1:09:47
Janelle,
First let me say that I am not really a neuropsychopharmacologist, I just play one on PSB!
You asked, "However, if acetylcholine is a *good* thing, why would a TCA be DESIGNED to block it, or is it an unwanted thing that a TCA blocks acetylcholine? I other words is the acetylcholine blockade an unwanted side effect of a TCA?"
TCAs were not designed - they were discovered. It was a serendipitous scientific discovery that these chemicals could relieve depression.
So if you are treating depression with a TCA, the anticholinergic properties are unwanted, unneeded side effects.
However if you are treating something else with a TCA, going "off-label" with the drug, the anticholinergic effects might be very useful.
My wife has a stomach condition called "IBS" and although all the tests show nothing wrong, she has terrible stomach pain, cramping, and diarrhea.
We went through months of trying different pills to stop the pain and diarrhea. We had to go to the ER every 3rd day for her to get IV fluids. She was even taking lots of Percocet, which usually kills any pain and causes terrible constipation, and it did not help.
Finally her GI doc suggested Elavil, a TCA. It worked almost immediately. The anticholinergic properties stopped the spasming of her intestines, which meant less pain, and Elavil also blocks serotonin.
Besides modulating mood in the brain, it turns out that serotonin modulates pain in the GI tract. So properties of Elavil that have nothing to do with its AD effects made it very useful for her IBS.
Take a look at this link:
http://www.preskorn.com/columns/9803.html
If fact, if you have time, Dr. Preskorn's entire site if just chock full of the stuff that you are asking so many questions about.
Here's the main link to Dr. Preskorn's site
http://www.preskorn.com/columns.html
> Fachad wrote in a thread further up that an anticholinergic drug, for example a TCA, binds to cholinergic receptors and keeps acetylcholine from acting there. Okay, so far, so good, I get this!
>
> However, if acetylcholine is a *good* thing, why would a TCA be designed to block it, or is it an unwanted thing that a TCA blocks acetylcholine? I other words is the acetylcholine blockade an unwanted side effect of a TCA?
>
> And this leads me to ask, just what are TCA's targeted to in the brain? (SSRI's prevent serotonin reuptake, what do TCA's do?)
>
> And one other thing - I'm not sure I'm getting the concept of the receptor - from the spelling of the word I associate it with *receiving*, so I come away with the idea that receptors receive things. Yet, when I read various threads on here explaining things, it sounds like receptors RELEASE things? What do receptors do? Ack ... I'm confused.
poster:fachad
thread:99599
URL: http://www.dr-bob.org/babble/20020322/msgs/99635.html