Our preliminary studies have indicated that the gamma-ray emitting analogs, 6-*Br-L-DOPA and p-*Br-Spiroperidol, are potentially active analogs of L-DOPA and Spiroperidol. The first objective of this proposal is to compare the behavior of these analogs "in vivo" with that of the neurotransmitter precursor 3H-L-DOPA and neuroleptic compound 3H-Spiroperidol in normal animals and in animals which have been lesioned or pharmacologically manipulated. For this purpose we will use in vitro and in vivo binding assays and study tissue distributions of the compounds. The second objective is to demonstrate that relevant neurological parameters can be obtained with these compounds using external gamma-ray imaging techniques. For this part of the study we will first delineate the utility of standard nuclear medicine imaging devices although the compounds can be made with Br isotopes suitable for positron tomography. In our final aim we will use the gamma-ray imaging technique and these compounds to assess the time course and extent of in vivo fiber degeneration following lesions as well as changes in dopamine receptors following lesions or drug administration. These results will determine the utility of the technique for assessing neuronal deficits over time by noninvasive, non-destructive means.