Posted by IsoM on March 23, 2002, at 22:04:36
In reply to FACHAD: re Serotonin and TCA's » fachad, posted by Janelle on March 23, 2002, at 20:40:50
Sorry, Janelle. This can be awfully confusing when you first learn but I've got to explain the context of "these neurotransmitters are confined to synapses in the brain". This is just talking about the context of the BRAIN only, & IN THE BRAIN, the only place serotonin is, is in the neural synapses.
When serotonin is found in other places in the body, it's not just confined to the synapses of nerves. I hope you can see this difference.
I hope this will help & not confuse you more. And when a person studies these things in university, remember, it's taken slow & easy with simple biology first & slowly becomes more complicated - building on a previous foundation of knowledge. Jumping in to learn just about brain biochemistry is going to make you feel like you're floundering at times. Don't give up! you're doing wonderfully, Janelle, & it'll all come together yet.
"The greatest concentration of 5HT (90%) is found in the enterochromaffin cells of the gastrointestinal tract. Most of the remainder of the body's 5HT is found in platelets and the CNS. The effects of 5HT are felt most prominently in the cardiovascular system, with additional effects in the respiratory system and the intestines. Vasoconstriction is a classic response to the administration of 5HT.
Neurons that secrete 5HT are termed serotonergic. Following the release of 5HT, a portion is taken back up by the presynaptic serotonergic neuron in a manner similar to that of the reuptake of norepinephrine.
The function of serotonin is exerted upon its interaction with specific receptors. Several serotonin receptors have been cloned and are identified as 5HT1, 5HT2, 5HT3, 5HT4, 5HT5, 5HT6, and 5HT7. Within the 5HT1 group there are subtypes 5HT1A, 5HT1B, 5HT1D, 5HT1E, and 5HT1F. There are three 5HT2 subtypes, 5HT2A, 5HT2B, and 5HT2C as well as two 5HT5 subtypes, 5HT5a and 5HT5B. Most of these receptors are coupled to G-proteins that affect the activities of either adenylate cyclase or phospholipase Cg. The 5HT3 class of receptors are ion channels.
Some serotonin receptors are presynaptic and others postsynaptic. The 5HT2A receptors mediate platelet aggregation and smooth muscle contraction. The 5HT2C receptors are suspected in control of food intake as mice lacking this gene become obese fromincreased food intake and are also subject to fatal seizures. The 5HT3 receptors are present in the gastrointestinal tract and are related to vomiting. Also present in the gastrointestinal tract are 5HT4 receptors where they function in secretion and peristalsis. The 5HT6 and 5HT7 receptors are distributed throughout the limbic system of the brain and the 5HT6 receptors have high affinity for antidepressant drugs."
poster:IsoM
thread:99599
URL: http://www.dr-bob.org/babble/20020322/msgs/99732.html