The crucian carp survives anoxia with the brain turned on. In such a state it is crucial to lower energy expenditures. This can be achieved by lowering the permeability of ionotropic receptors such as the N-metyl-D-aspartate receptor (NMDAR). We hypothesized that the crucian carp NMDAR possess properties important for anoxic tolerance. This thesis reports the full-length cloning of the NR1 subunit, as well as ESTs for NR2A-D and NR3A in crucian carp. Phylogenetic analyses supported the identity of all subunits, and suggested the finding of two closely related paralogs for NR1, NR2A and NR2D. These paralogs provide evidence for a recent genomic duplication event in the crucian carp lineage. Protein analyses of NR1 revealed no obvious adaptations important for anoxic survival. All key properties were conserved. However, a novel splice cassette, ‘NTSG’, was found in the N-terminal. This was predicted to represent a functional N-glycosylation site. Real-time RT PCR primers were designed for assessments of gene expression.