What about taurine?

"Taurine is an amino acid that can be made in your body from two other amino acids: cysteine and methionine...

"A facilitator for the passage of sodium, potassium and possibly calcium and magnesium ions into and out of cells."
http://www.drlwilson.com/Articles/TAURINE.HTM

"taurine can replace some of magnesium's functions when magnesium is deficient. . . Both nutrients exert sedative effects and lower the excitability of nerve cells."

http://www.studio41.co.nz/Community/...-of-magnesium/

I don't know if magnesium taurate is made with the right ratio (I take my Mg and Taurine separately).

There's not much research on humans yet, but there has been some success with rats.

"Studies have shown taurine can influence (and possibly reverse) defects in nerve blood flow, motor nerve conduction velocity, and nerve sensory thresholds in experimental diabetic neuropathic rats."

http://en.wikipedia.org/wiki/Taurine

It seems pretty safe from what I've read so I take it every day, esp. because I don't eat much meat, which causes a taurine deficiency.

P.S. It's good for cat eye health.