Posted by BarbaraCat on March 26, 2002, at 16:38:38
In reply to SO, AM I RIGHT?!!??, posted by Janelle on March 26, 2002, at 14:30:04
Janelle,
Rather than there being many 'pumps', think many 'receptors'. There are few pumps, but many different receptors. Each transport pump can recycle many neurotransmitter molecules. Pumps are little workhorses and take care of a whole lot of transmitters and are not really choosy about which ones they're transporting, just as long as they get deposited back to the shores of the axon end. Kind of like the synaptic gap is an ocean between two shores and the reuptake pump is a ferry boat that can transport many people from the middle of the ocean back to the starting shore.An electrical spike fires down the long arm (axon), the 'sending' end of a neuron and releases the many different kinds of neurotransmitters into the synaptic cleft. Neurotransmitters are sent across this gap and received into their respective receptors on the membrame of another neuron. Receptors are large protein molecules that are embedded in the membrane of the receiving end of a neuron. The receptors fill up, change shape, an action potential is created causing an electrical spike to be sent down the axonal arm - to be repeated on and on. Whatever transmitters weren't used can get destroyed by other enzymes, so the reuptake pump removes them from the gap and deposits them into a safe holding area - the vesicles - which are sacks within the terminal end of the axon.
A neurotransmitter can occupy several different subtypes of receptors. Serotonin has at least 5 different kinds of receptor subtypes, dopamine at least 5, etc. To complicate matters further, each neuron has many terminating branches of an axon that look like a tree, each with it's own synapse, etc.
Some SSRI's target specific receptors which is why it's so tricky to get the right drug the first time. So many variables. BUT it's not only reuptake pumps that are implicated in SSRI's .
Recent research states that AD's work primarily by decreasing the number of the targeted receptors making the available neurotransmitters more efficient. And neurotransmittors are only the beginning - they're known as the 'first messenger system' in that they activiate something called a G-protein which is one of the components of DNA (guanine). G-protein then activates the second messenger system and this system is probably the most important one of all in that it regulates the DNA expression of genes, the structure of the cells, and the synthesis of transmittors in the first place - the underpinnings of the whole thing. Whew! What a work is man! - BCat
> Thanks for confirming that there ARE many, many serotonin reuptake pumps in the brain ... so now am I right that the different *brands* of SSRI's (e.g. Prozac, Zoloft, Paxil, Celexa, etc.) target DIFFERENT pumps?
>
> And this could be why one of the SSRI's, let's say Prozac, will benefit Person A but not Person B because Person A needs the pumps affected by Prozac, whereas Person B needs the pumps that are affected by one of the other SSRI's? I hope I'm making this clear?!
poster:BarbaraCat
thread:100140
URL: http://www.dr-bob.org/babble/20020322/msgs/100332.html