DOPAMINE D-2, D-3, AND D-4 RECEPTOR MESSENGER-RNA LEVELS IN RAT-BRAINAND PITUITARY DURING AGING

Reverse Transcriptase-Polymerase Chain Reaction technique was used to determine the levels of the mRNAs encoding different receptors belongi ng to the D-2 family in various brain areas of 6-, 12-, 18-, and 24-mo nth-old rats. We found a progressive, age-dependent reduction in the m RNA levers of D-2 short and D-2 long receptors in corpus striatum, sub stantia nigra, and frontal cortex. D-2 short and D-2 long receptor mRN A levels were unchanged in hippocampus and olfactory tubercle, while t hey increased in pituitary. D-3 receptor mRNA levels were reduced in o lfactory tubercle and unchanged in striatum. D-4 receptor mRNA levels were unmodified in pituitary gland. These data suggest that the molecu lar mechanisms responsible for regulating the pattern of expression of the various dopamine receptors are differentially regulated by aging.