The first part of this book describes current work on the actions of hypothalamic releasing factors and nerve growth factor from the characterization of their cell surface receptors to the mechanisms of signal transduction leading to cellular response. The second part considers the actions of gonadal steroids and glucocorticoids on neurons. Success in the cellular localization of steroid receptors and specific gene products that are regulated by steroids has significantly increased our knowledge of the organization of the brain and the integration of responses to endocrine signals that lead to behavior. The third part considers current research on magnocellular neurons. Studies of magnocellular neurons have, over the years, provided the framework for concepts of synthesis, storage, and secretion of neuropeptides. The three articles in this section treat recent advances in the understanding of the molecular biology of the oxytocin gene, posttranslational events, and the electrophysiology of magnocellular neurons. The information emerging from neuroendocrine studies using the experimental approaches characterized in this volume is paving the way for more refined experimentation which will lead us toward an understanding of brain function at the molecular level.