Several series of experiments are planned in continuing work on two neural peptides, substance P and neurotensin, that have been isolated, sequenced, and synthesized in this laboratory. The studies outlined include a) mapping the distribution of these peptides in brain and peripheral nerve. b) delineation of substance P or neurotensin-containing tracts within the central nervous system. c) the release of substance P and neurotensin from neural tissue in vitro and in vivo. d) the chemical characterization of substance P and neurotensin in plasma. e) manipulation of the plasma levels of immunoreactive substance P and neurotensin.