l-homocysteic acid ( l-hca ) has been proposed as a natural transmitter at the n-methyl-d-aspartate ( nmda ) subtype of excitatory amino acid receptor based on recent evidence that l-hca occurs l-hca occurs naturally in the mammalian cns , is released from k+ stimulated brain slices in a calcium-dependent manner and may be contained in nerve terminals located in certain brain regions that have a high density of nmda receptors .
C3714787
cns
C0006104
brain