With the use of quantitative autoradiography, we studied the role of neuropeptides (angiotensin II, atrial natriuretic peptide) and biogenic amines (dopamine) in the central regulation of autonomic nervous system and pituitary gland. We also studied the role of neuropeptides in the regulation of the immune response by localizing neuropeptide receptors in immune organs and immune cells and by investigating the second messenger response. We demonstrated a role for central angiotensin II and atrial natriuretic peptide in the control of cardiovascular function. These neuropeptides may also be involved in regulation of the immune response. Specific angiotensin II and beta-adrenoceptors were quantified in the rat heart conduction system. New methods were developed to study localization and transport of D1 and D2 dopamine receptors in brain, and to study localization of malignant melanomas. Psychotomimetic phenylisopropylamine receptors were localized and quantified in selective brain areas.