Monoamine transporters are the targets of brain imaging agents, antidepressant drugs, cocaine, and methylphenidate, the most effective drug for treating attention-deficit disorder. This Division has an ongoing program to develop novel therapeutic and imaging agents for neuropsychiatric disorders. To identify promising therapeutic or imaging agents that target transporters, it is necessary to first investigate the binding properties of the compounds in vitro and determine their affinity and transporter specificity. Based on data from these experiments, candidate drugs progress through a series of other in vivo tests in nonhuman primates, and if warranted into clinical trials. The goal of this pilot project is to develop stable cell lines that express non-human primate dopamine, norepinephrine and serotonin transporter cDNA. These stable cells lines will be used for at least three purposes. 1. to investigate novel drugs (designed as imaging agents or as therapeutics) in a preparation that is potentially less hazardous to human health than monkey brain tissue. 2. To compare the sequence homology of squirrel monkey dopamine transporter and human transporter. 3. to determine evolutionary changes monkey vs human transporters. In brain tissue, the squirrel monkey and the human transporters bind cocaine with higher affinity than the transporter of macaque monkeys and we will investigate whether amino acid sequences account for these differences. We will clone dopamine transporter cDNAs from old-world and new-world monkey using a reverse transcriptase-polymerase chain reaction strategy, based on the high degree of similarity between the cloned mammalian dopamine transporter sequences. RNA will be extracted from monkey substantia nigra using a Poly(A)Pure mRNA purification kit. These cell lines will provide a resource for screening potential imaging agents in vitro that is not dependent upon the availability of monkey brain tissue, have greater consistency from experiment to experiment, and are less