N-Methyl-image-Aspartate Receptor Binding in Brains of Rats at Different Ages

Potential age differences in N-methyl-image-aspartate (NMDA) receptor binding were evaluated in rat brain using [3H]dizocilpine and [3H]image,image-(E)-2-amino-4-propyl-5-phosphono-3-pentanoic acid (CGP 39653) as the radioligands. Neither [3H]dizocilpine nor [3H]CGP 39653 binding in hippocampus revealed any age difference (7 vs. 23–25 months) in Bmax or Kd. High-affinity [3H]dizocilpine binding showed a developmental increase (8 vs. 2 months) in hippocampus but not in frontal cortex. No senescence-related change (25 vs. 8 months) was observed in either region. The lack of senescence-related differences in these biochemical markers does not preclude the possibility of functional changes in the NMDA receptor with aging.