Richard J. Bodnar is professor and chair of the Department of Psychology at Queens College of the City University of New York. Kathryn Commons is a postdoctoral fellow in the Laboratory of Neurobiology and Behavior at the Rockefeller University. Donald W. Pfaff is professor and head of the Laboratory of Neurobiology and Behavior at the Rockefeller University. He is a fellow of the American Academy of Arts and Sciences and a member of the National Academy of Sciences.

• Contents: Series Foreword Preface List of Abbreviations I Requirement for Motivational State Concepts A Physics, Brain, and Behavior B Motivation in Its Generalized and Specific Aspects C Motivation for Females to Seek Males D Hypothalamic and Preoptic Mechanisms Involved in Two Types of Motivational Change E Summary II Ascending Arousal Systems Activated A Ascending Reticular Activating Systems B Structure of Arousal States C Application to Sexual Behavior D Clinical Observations on Human Awareness and Arousal E Mood F Summary III Descending Systems: The Importance of Opioid Peptides and Analgesia A Opioid Peptides in Pain and Analgesia B Analgesia Induced by Stress and Environmental Variables C Hormonal Control of the Enkephalin Gene: One Paradox and Three Solutions D Intimate Relations among Inhibitory Systems E Hypothalamic Projections F Gender Differences in Analgesia G Pain and Sex: Similarity of Reproductive Behavior and Analgesia - Ascending and Descending Pathways H Summary IV Inferences and Arguments A Gene/Behavior Relationships: Application to Opioid Peptides B Biological Importance of the Relations among Sex, Arousal, and Analgesia References Index