The present project aims at the elucidation of the biochemical individuality of neurons and affiliated neuroendocrine elements on a comparative basis. The experimental invertebrate model of choice will be the blattarian insect Leucophaea maderae. The investigation will be based primarily on the use of immunocytochemical techniques with both monoclonal and polyclonal antibodies. (a) One part of the program will be an expansion of our long-range studies concerned with neuroendocrine phenomena and bioactive neuropeptides. The availability of antibodies to the impressive list of such neuropeptides known to date will provide valuable information on the occurrence and putative functions of vertebrate-type neurochemical messengers, such as insulin, in insects. Special attention will be given to the differential localization of reaction products in various domains of the neural and neuroendocrine apparatus judged to be indicative of diverse functional roles. (b) The second part of the program will carry the search for biochemical individuality in invertebrates beyond that expressed by the multiplicity of peptidergic neuroregulators. It will focus on the detection of heterogeneity among the structural proteins of insect neurons by screening tests with monoclonal antibodies raised against individual mammalian molecules. These will include probes for special protein fragments identifying neurofilaments, and others characteristic of certain cells associated with the immune system.