Posted by SLS on June 4, 2009, at 15:02:34
In reply to Can somebody explain this to me please?, posted by Meltingpot on June 4, 2009, at 11:27:55
> Hi,
>
> I am hoping that somebody will be able to explain the below paragraph to me. Does this mean that the dopamine transporter on the Presynaptic neurone takes up the serotonin rather than the 5HT transporter which is being blocked by the SSRI?
>
> If this is the case wouldn't that negate the effects of the SSRIs?
>
> I get a bit confused by the indirect affects of antidepressants and I'm trying to get my head around it all.
>
> thanks.........Denise
>
> Now, however, Fu-Ming Zhou (presently at the University of Tennessee) and colleagues at Baylor College of Medicine have revealed that SSRIs can have more complex effects on neurotransmitter traffic in the brain than just altering serotonin levels. They found that higher serotonin concentrations caused by SSRIs can "trick" transporters of another key neurotransmitter, dopamine, into retrieving serotonin into dopamine vesicles. Dopamine transporters have a low affinity for serotonin, but the higher serotonin levels result in its uptake by the dopamine transporters, found the scientists.
Hi Denise.In this case, serotonin is acting as a false transmitter. It is succeeding as a competitive ligand for the presynaptic dopamine neuron simply because there is such a high concentration of it compared to the normal levels of dopamine. Apparantly, the DA transporter, while being selective for dopamine, is not specific enough for it to prevent some from getting into the dopamine neurons. Once inside the neuron, serotonin is taken into the synaptic vesicles just as easily as the dopamine is. Once released, the serotonin is incapable of stimulating the postsynaptic DA receptors. The bottom line is that serotonin displaces dopamine, and thus might provide a basis for diminished DA activity along certain pathways. Although this is not dopamine depletion from overuse, it might as well be if the net effect is the same. It must be noted, however, that this is still an acute effect of the SSRI. Chronic exposure actually increases DA activity along many pathways.
- Scott
poster:SLS
thread:899383
URL: http://www.dr-bob.org/babble/neuro/20090129/msgs/899398.html