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What Part Of Brain Does Bupropion Affect? Frontal Cortex? Staitum?


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#1 CrashTstDummy

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Posted 17 October 2008 - 12:21 PM

I'm asking because I'm currently taking Ritalin, - which pumps up the dopamine and adrenalin in one's staitum (mid part of brain).

But when I take the Ritalin, I feel a spaciness or vapidness in the front of the brain, so I am curious whether Wellbutrin acts on the prefrontal cortex, or whether it will simply be another drug - ala Ritalin - that amps up the Staitum, and leaves the rest of my brain feelings empty?

Thanks you much!

#2 inverse_agonist

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Posted 17 October 2008 - 07:22 PM

Ritalin (methylphenidate) and Wellbutrin (bupropion) both block the reuptake transporters for dopamine and norepinephrine. Dopamine is released in both prefrontal cortex and the entire striatum. Norepinephrine is not released in most of the striatum at all, only the "ventral striatum," also called the nucleus accumbens. Norepinephrine is released basically everywhere in the brain, except certain parts of the basal ganglia (which the striatum is part of).

Ritalin and Wellbutrin have basically the same mechanism, but Ritalin is more potent. An average person might take 30 mg of Ritalin in a day, while an average Wellbutrin user would take 300 mg of Wellbutrin per day, 10 times as much. Another difference between the drugs is that Wellbutrin blocks certain nicotinic acetylcholine receptors, which is why it is also used to help people stop smoking.

Norepinephrine-releasing cells all have norepinephrine transporters, so taking either drug will increase the amount of norepinephrine floating around in both prefrontal cortex (and the rest of cortex) and the nucleus accumbens. The dopamine system is different. Dopamine cells that project to the striatum have dopamine transporters, but dopamine cells that project to prefrontal cortex do not. Confusingly, dopamine released into prefrontal cortex is taken up by norepinephrine neurons, through the norepinephrine transporter. Therefore, both drugs increase dopamine levels in the striatum by blocking the dopamine transporter, and increase dopamine levels in prefrontal cortex by blocking the norepinephrine transporter.

It works this way because norepinephrine is made from dopamine. Adrenaline in turn is made from norepinephrine, but that mostly happens way down in the brainstem and in the adrenal glands above your kidneys. There isn't much adrenaline in the brain itself.

Because Ritalin is "stronger" than Wellbutrin (based on both dose and how much the transporters are affected by them), Wellbutrin feels a lot less stimulating after the first week or so of taking it. Wellbutrin can be used off-label for ADHD, but taking it more regularly is probably more like being on Strattera (atomoxetine) than being on Ritalin. The effects of all of these drugs on attention, memory, etc. are related to receptors for both dopamine and norepinephrine in prefrontal cortex. It's hard to say exactly which ones, because all of these drugs increase the levels of both dopamine and norepinephrine (there are ways of getting around this with more exotic drugs or with mutant mice).

In general, it's very rare that a drug will affect only one part of the brain. Most types of receptors are found in more than one place, which is where some of the side effects from drugs come from. The medically useful effect of Ritalin is in prefrontal cortex, but Ritalin also changes things in the nucleus accumbens, which is why it can be addictive, for example.

The striatum is actually in the forebrain (telencephalon), but its dopamine input comes from groups of cells in the midbrain (substantia nigra pars compacta and ventral tegmental area). You can't really tell where in the brain a mental event is happening based on how it "feels." If you could, people wouldn't need to spend ridiculous amounts of money to do fMRI studies.

However complicated you think a drug's mechanism of action is, it's probably more complicated than that :-).



I'm asking because I'm currently taking Ritalin, - which pumps up the dopamine and adrenalin in one's staitum (mid part of brain).

But when I take the Ritalin, I feel a spaciness or vapidness in the front of the brain, so I am curious whether Wellbutrin acts on the prefrontal cortex, or whether it will simply be another drug - ala Ritalin - that amps up the Staitum, and leaves the rest of my brain feelings empty?

Thanks you much!



#3 Burgy

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Posted 17 October 2008 - 07:30 PM

:blink:


Posted Image We are what we think. All that we are arises with our thoughts. With our thoughts, we make the world. ~Buddha




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