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Dr. Bob is Robert Hsiung, MD,
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Posted by iforgotmypassword on September 4, 2005, at 21:17:18
causes lower density of DA1 and DA2 type receptors:
http://www.selegiline.com/phenylethylamine.htmllack of effect in mesolimbic dopamine system:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8278449&query_hl=1if its a pro-dopamine/frontal cortex drug how does this make sense?
Posted by linkadge on September 5, 2005, at 8:46:08
In reply to paradoxical information about selegiline, posted by iforgotmypassword on September 4, 2005, at 21:17:18
How is this paradoxical? These findings do not condradict earlier findings suggesting the drug increases frontal cortex dopamine content.
The reductions in the d1, d2 receptors are consistant with most dopaminergic drugs. Just like the SSRI's cause downregulation in certain serotonin receptors. Downregulation is indicitive of greater functionality of the dopamine system.
Linkadge
Posted by iforgotmypassword on September 5, 2005, at 9:00:37
In reply to Re: paradoxical information about selegiline, posted by linkadge on September 5, 2005, at 8:46:08
isn't it just downregulation of the autoreceptors thats beneficial though? i thought one of the late effects of antidepressants was to increase D2 receptor density to actually be effective against anhedonia.
Posted by Schess81 on September 5, 2005, at 9:46:39
In reply to paradoxical information about selegiline, posted by iforgotmypassword on September 4, 2005, at 21:17:18
I have a somewhat similiar question about any dopaminergic- because the positive effect on motivation and anhedonia would be immediate, wouldn't the body eventually develop tolerance by downregulating the DA receptors? (Maois, stimulants etc)
Posted by linkadge on September 5, 2005, at 10:00:21
In reply to Re: paradoxical information about selegiline, posted by iforgotmypassword on September 5, 2005, at 9:00:37
Hmm,
I am not entirely sure. I think that it is dependant on the region. The study says that other MAOI antdidepressants (phenylzine) induced a decrease in the density of d1 d2 receptors in the stratium.
It does not mention the effects on the d1 d2 receptors in the neucleus accumbens.
For instance the below study suggests that AD treatment increases dopamine d1/d2 receptor density in the neucleus accumbens, but decreased the level of dopamine in the NAA.
http://biopsychiatry.com/dopamine.htm
It might be necessary to find how deprenyl affects d1/d2 receptor binding in the NAA specifically.
Linkadge
Posted by linkadge on September 5, 2005, at 10:19:05
In reply to Re: paradoxical information about selegiline, posted by Schess81 on September 5, 2005, at 9:46:39
I would assume that if you are anhedonic then tollerance to restorative effects of the drug are less likely.
If the drug drives the dopaminergic system above what is normal then tollerance is more likely.
Linkadge
Posted by linkadge on September 5, 2005, at 10:20:33
In reply to Re: paradoxical information about selegiline, posted by iforgotmypassword on September 5, 2005, at 9:00:37
This study says that repeated desipramine decreases d1,d2 responsiveness in the stratium, wheras the previous study said that it increases d1/d2 responsiveness in the neucleus accumbens.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8130732&dopt=Abstract
So I think it may depend on the region.
Linkadge
This is the end of the thread.
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