Aging-related changes in rat striatal D2 receptor mRNA-containing neurons: a quantitative nonradioactive in situ hybridization study.

In situ hybridization of a digoxigenin-labeled oligonucleotide probe combined with computer-assisted image assessment was used to directly visualize D2 receptor mRNA-containing neurons in rat striata, and quantify age-related changes in the sizes and relative mRNA content of these neurons. It was found that: (1) numbers of D2 mRNA-containing neurons appear to decrease in striata of aged rats, (2) relative amounts of D2 receptor mRNA decrease in striatal neurons of aged rats, and (3) neurons of all sizes appear to be lost, with the greatest absolute decrease in those smaller than 90 microns 2. These data confirm the well documented age-associated loss of D2 dopamine receptors, and further suggest that both neuronal death and reduced transcription contribute to this decrement.