[3H]MK-801 binding sites in neonate rat brain.

[3H]MK-801 binding sites are present in neonate rat brain as early as 3 days after birth. Immature hippocampus and cortex contain approximately one sixth the concentration of binding sites of the adult, while brainstem concentration is twice as high as that of adult. [3H]MK-801 binding is stimulated by glutamate and glycine and blocked by phencyclidine and Mg2+ both in 7-day-old neonate and adult, indicating that as early as 7 days postnatally, the N-methyl-D-aspartate-type glutamate receptor and MK-801 binding site are functionally coupled.