Advances in Vagal Afferent Neurobiology PDF

Preface

Vagus is a Latin word with a root that also gives us the term vague . This is appropriate, as much of what we know about vagal sensory neuroscience remains vague and imprecise. This is partly due to a decided lack of information. The number of scientific studies aimed directly at investigating the primary afferent nerves within the vagi pale in comparison with the somatosensory nerves of the dorsal roots. Given the pivotal role they play in visceral physiology as well as pathophysiology, one could reasonably argue that vagal sensory nerves are relatively understudied by today's standards. As a surrogate for direct information, it is often tempting to infer knowledge about vagal afferent nerves from the many elegant studies carried out on somatosensory nerves. Beyond some basic fundamental principles, however, this practice may lead to more confusion than clarity. This is because sensory nerve phenotype is directed from embryological "top down" signals as well as from tissuederived "bottom up" signals. The vagal sensory neurons have their own unique embryological history and the tissues within the visceral organs they innervate provide another set of signals that render the nerves dissimilar in many ways to their somatosensory cousins.

Also contributing to the lack of focus in vagal neuroscience is the fact that investigators in this field are spread across many disciplines. The vagus meanders through the viscera, providing important regulatory influences over the thoracic and abdominal organs. This leads to a situation in which experts in vagal neurobiology are often "organo-centric" presenting their work in organ-specific journals and discussing their findings within their own organ-specific meetings. One of the purposes of this book is to present coherent summaries of vagal afferent neuroscience obtained within the body's organ systems. By juxtaposing these chapters in a single text, it is anticipated that cross-fertilization of ideas will provide new insights and focus on this important topic.

In Latin, the term vagus also means wandering. In this context, this book can be considered vagal . There have been outstanding resources published on specific aspects of vagal neuroscience, but there are few, if any, publications that provide a broad overview of vagal sensory neurobiology. With this in mind, this volume has been designed with chapters that wander through all aspects of vagal sensory nerve biology. This occurs on a lateral scale with chapters that deal with vagal nerves in the central nervous system (CNS), lungs, esophagus, heart, and gastrointestinal tract. The book also wanders on a vertical scale as it covers critical aspects ranging from vagus nerves in the embryo to vagus nerves in the adult, and from activity in individual neurons to whole animal studies of the reflexes and sensations such activity engenders. It is hoped that by painting vagal afferent biology with the broadest brush possible, this book will be a unique and useful resource for the student, as well as for the established neuroscientist interested in the visceral nervous system.

Such nonreductionism runs the risk of failing for lack of discriminating detail. This is not the case here. In each chapter, experts cover a particular area of vagal afferent neuroscience. The authors provide an overview of the given topic and, in many cases, details pertaining to specific experiments and techniques. This approach has resulted in an informative reference for the vagal sensory neurobiologist.