Vitamin B12- found in beef, liver, chicken, clams, and tuna. “Protective effects of methylcobalamin, a vitamin B12 analog, against glutamate-induced neurotoxicity in retinal cell culture. Chronic administration of methylcobalamin protects cultured retinal neurons against N-methyl-D-aspartate-receptor-mediated glutamate neurotoxicity, probably by altering the membrane properties through SAM-mediated methylation.” https://www.ncbi.nlm.nih.gov/pubmed/9112980 “Vitamin B12 enhances GABA content but reduces glutamate content in the rat suprachiasmatic nucleus.” https://www.ncbi.nlm.nih.gov/pubmed/9249572