Hi Ruchira:

Check this one:

http://www.nejm.org/doi/pdf/10.1056/NEJM199403033300901

Best

meanwhile there are a lot of publications available (since 1994)

first one:

Bensimon et al. N Engl J Med 1994; 330: 585-91

see the paper by virginia le Verche , B Ikiz, A Jacquier, S. Przedborski and D B Re 

J receptor, ligand and channel Research 

4, 2011, 1-22. Glutamate pathway implication in amyotrophic lateral sclerosis: what is the signal in the noise ?