The mechanism(s) underlying age-associated diminutions in the rat striatal D2 dopamine receptor (D2-receptor) number was investigated. The levels of D2-receptor mRNA in 4-, 12- and 18-month-old rat striata were found not to change. In contrast, the levels of 110 kDa protein, labeled with a D2-receptor specific antibody, decreased in parallel with [3H]YM-09151-2 binding to striatal membranes. These data suggest a role for post-transcriptional mechanism(s) in age-associated decrease in D2-receptor.