A pilot study was completed in both rhesus and squirrel monkeys to determine the efficacy of the DSP-4 injection. Thirty days following injection, monkeys were euthanized and brain sections were analyzed for noradrenergic depletion. In the regions of interest, there was 60-75% depletion confirming the effectiveness of the DSP-4. Subsequently, a longitudinal study was initiated first in squirrel monkeys. Monkeys received an initial dose and a booster dose at 3 and 6 months and were terminated at 9 months. Quantification of the noradrenergic depletion is underway. The parallel study in rhesus monkeys is ongoing with an additional measure of learning and memory.