The subject of this book is neuroendocrinology, that branch of biological science devoted to the interactions between the two major integrative organ systems of animals-the endocrine and nervous systems. Although this science today reflects a fusion of endocrinology and neurobiology, this synthetic ap proach is relatively recent. At the beginning of the 20th century, when the British physiologists, Bayliss and Starling, first proposed endocrinology to be an independent field of inquiry, they went to great lengths to establish the autonomy of chemical secretions in general and their independence from nervous control in particular (Bayliss, W. M. , and Starling, E. H. , 1902, The mechanism of pancreatic secretion,]. Physiol. 28:325). They argued with Pav lov, who said that there was a strong influence of the nervous system on the gastrointestinal phenomena the endocrinologists were studying. For several decades, the English physiologists prevailed, at least in the West; and Pavlov's critique was not taken to heart by the practitioners of the newly emerging discipline of endocrinology. Through the work of Harris, the Scharrers, Sawyer, Everett, and others, there has been something of a scientific detente in the latter half of this century; the hybrid field of neuroendocrinology is now regarded as one of the corner stones of modern neural science and is of fundamental importance in basic and clinical endocrinology.

The subject of this book is reproduction-specifically, the interplay between reproductive physiology (especially neural and endocrine events) and behavior. In presenting this topic, there are two expository goals. The first is to study repro- duction at all of the major levels of biological organization-from the molecular (e. g. , hormone receptors in the brain), through the cellular (e. g. , ovarian morphogene- sis), systemic (e. g. , operation of the hypothalamo-pituitary-ovarian axis), and the organismic levels of organization. Analogously, behavior is treated from the most molecular, elementary, and fundamental components (e. g. , copulatory reflexes), through behavior in the reproductive dyad (e. g. , analysis of female sexual behav- ior), to complex social behavior (e. g. , the interaction of social context and behav- ioral sex differences). To the extent that these levels of biological and behavioral organization rep- resent a "vertical axis" in behavioral neurobiology, a second goal is to treat the "horizontal axis" of biological organization, viz. , time. There are, therefore, treat- ments of evolutionary origins (e. g. , a phylogenetic survey of psychosexual differ- entiation), genetic origins in the individual (e. g. , sexual organogenesis), ontoge- netic development (e. g. , behavioral sexual differentiation), and the immediate physiological precursors of behavior (e. g. , hormonal and nonhormonal initiation of maternal behavior). In addition to tracing the origins of reproduction and reproductive behavior, one extends the time-line from the behavior to its physio- logical consequences (e. g. , neuroendocrine consequences of sexual behavior).