Ah, but don't forget about diseases like PKU which is defined by a decreased ability to take up tyrosine from the blood (a precursor of dopamine). PKU certainly can result in abnormalities in brain function if proper dietary restrictions are not followed (i.e., a tryptophan restricted diet).
A nice example/elaboration about how the same chemical can serve two quite distinct functions is the role of histamine in the body. Histamine acts on H1 receptors to elicit the common "symptoms" of an allergic response (thus antihistamines, like chlorpheniramine, will "block" this response). On the other hand, the same histamine molecule acts at the H2 receptor in the gastric mucosa to elicit gastric acid secretion (thus H2 antagonism using drugs like Tagamet and Pepcid are indicated for ulcers and gastric acid over-secretion problems). I further explain that taking Tagamet for allergies is non-effective. Likewise, taking chlorpheniramine for ulcer is ineffectual. Students seem to "like" these examples because they're somewhat familiar with the responses and the common drugs used. Like serotonin, histamine seems to be very useful physiologically, so "the body uses the molecule" in more than one place. BTW, histamine and serotonin are also chemically quite similar molecularly, both belonging to the indolamine family. And in addition to all this cool stuff, histamine is a putative neurotransmitter in the brain (at a receptor sometimes referred to as the H3 receptor). More than you ever wanted to know about histamine, I'm sure. David Epstein wrote: > On Wed, 3 Sep 2003, Nathalie Cote went: > > > One of my Intro Psych students told me that he found a Web site that > > says that the gastrointestinal tract is a bigger producer of serotonin > > than the brain is > > That's what I've been taught--that 90% of the body's serotonin is in > the gut, where it serves functions related to intestinal motility. > > > The student is concerned because he has had his colon removed for > > medical reasons, so he wants to know if that affects serotonin > > levels in his brain. > > No, there's nothing to worry about there. Serotonin doesn't penetrate > the blood-brain barrier, so the student's digestive tract can make as > much (or as little) serotonin as it likes, and his brain won't know > the difference, so to speak. > > Serotonin in the brain is made in specific clusters of neuron in the > brainstem, whose axons form specific pathways with specific (perhaps > even opposing) functions in various other brain regions. It's not > something that the brain needs to be globally bathed in, like > cerebrospinal fluid, and more isn't necessarily better. > > > 1) What do you know about serotonin in the gut? Other than being the > > same chemical, is it related to serotonin in the brain? How? > > I think that when nature finds a useful signaling molecule, it uses > that molecule wherever it can. So the same molecules tend to turn up > in a lot of different places; that doesn't have to mean they're > serving the same functions. > > > 2) The Web site above also makes the claim that "inadequate levels of > > serotonin and norepinephrine precursors in the diet > > ...probably constitute a condition that almost never occurs. > > > is it the case that extended use of SSRIs depletes > > neurotransmitters? > > No--at least, it's never been demonstrated. There are studies showing > that huge overdoses of SSRIs can damage serotonergic axons in rats. > Those studies have no implications for chronic use of therapeutic > doses. > > > And is it the case that diet has a measurable effect on > > neurotransmitter levels in the brain? > > Generally not, unless you go to unusual lengths, such as fasting, then > drinking specially made cocktails of amino acids from which tryptophan > is deliberately excluded. > > --David Epstein > [EMAIL PROTECTED] > > --- > You are currently subscribed to tips as: [EMAIL PROTECTED] > To unsubscribe send a blank email to [EMAIL PROTECTED] -- |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| Steven M. Specht, Ph.D. Associate Professor of Psychology Department of Psychology Utica College Utica, NY 13502 (315) 792-3171 "unanswered questions are less dangerous than unquestioned answers" --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
