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Why is magnesium an NMDA antagonist?

by mycotheology
Tags: antagonist, magnesium, nmda
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mycotheology
#1
Sep1-12, 05:03 PM
P: 90
The NMDA receptor is a ligand gated non selective cation channel. It allows Na+ and to a lesser extent Ca2+ and K+ to pass through. I read that Mg2+ clogs up the pore. Why would Mg2+ block the channel but not Ca2+? Ca2+ is larger so I'd expect that to be more likely to block an ion channel. Is it because Mg2+ is more electronegative than Ca2+?
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chill_factor
#2
Sep1-12, 11:43 PM
P: 899
Quote Quote by mycotheology View Post
The NMDA receptor is a ligand gated non selective cation channel. It allows Na+ and to a lesser extent Ca2+ and K+ to pass through. I read that Mg2+ clogs up the pore. Why would Mg2+ block the channel but not Ca2+? Ca2+ is larger so I'd expect that to be more likely to block an ion channel. Is it because Mg2+ is more electronegative than Ca2+?
I'd say its because Mg2+ is the smallest charge 2 ion and is more reactive than Ca2+; clogging up the pore might just mean that it deactivates the protein, not actually block the pore, right? Just my opinion, I'm no expert.
mycotheology
#3
Sep2-12, 04:31 AM
P: 90
Heres a quote from an abstract:
Physiological concentrations of magnesium reduce responses to N M D A by blocking the NMDA-associated ionophore in a voltage-dependent manner [2].
deepblue.lib.umich.edu/bitstream/2027.42/28723/1/0000544.pdf

In a voltage dependent manner so what you said must be correct. Magnesiums size-charge ratio is behind it. I read something about NMDA receptors being partially voltage gated.


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