Given the task definition and input, reply with output. In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

The effect of the NMDA - receptor antagonist ( + / - ) - CPP on the conditioned - reflex activation of an operant reaction in the brain electrical self - stimulation test in rats
NMDA - receptor