Posted by mtdewcmu on January 3, 2010, at 8:57:01
In reply to Re: Remeron + Paxil: so far, so good... or is it? » mtdewcmu, posted by SLS on January 3, 2010, at 7:45:42
> > > > Well, my mood is improving, but my bowels are tied in a knot again. So much for Remeron and its 5-HT3 inhibition...
> > >
> > > I hadn't heard of this theory. What is it all about?
> > >
> > >
> > > - Scott
> >
> > There are 5-HT3 receptors in the gut, and apparently they are responsible for a lot of the GI side effects of SSRIs. Remeron blocks them.
>
>
> Does that include peristalsis? I know that ondansetron has no such effect.
>Here is a bit from Goodman & Gilman (I hope I'm not violating the copyright):
"Motility of gastric and intestinal smooth muscle may be either enhanced or inhibited via at least 6 subtypes of 5-HT receptors (Table 112). The stimulatory response occurs at nerve endings on longitudinal and circular enteric muscle (5-HT4), at postsynaptic cells of the enteric ganglia (5-HT3 and 5-HT1P), and by direct effects of 5-HT on the smooth-muscle cells (5-HT2A in intestine and 5-HT2B in stomach fundus)."
So 5-HT3 has a stimulatory effect. I may have remembered the table slightly incorrectly; it says that 5-HT3 causes release of 5-HT from enterochromaffin cells in the GI mucosa and it causes fast depolarization of enteric ganglion cells; 5-HT2A is listed as causing contraction of intestinal smooth muscle. 5-HT2B and 5-HT4 are listed as causing contraction of the stomach fundus and esophagus, respectively. So that would explain why mirtazapine has a greater relaxing effect on the bowel than ondansetron.
Thanks for getting me to look that up and correct my memory.
> What did you mean when you described yourself as being tied in knots?
>It's just my bowel that feels that way, not my whole body. I have a sensation in my lower abdomen that feels like a cramp due to sustained contraction of the bowel, and apparently that's exactly what it is.
> Thanks.
>
>
> - Scott
poster:mtdewcmu
thread:931562
URL: http://www.dr-bob.org/babble/20100103/msgs/932282.html