Posts Tagged ‘Stress’

Stress: Neurobiology and Neuroendocrinology

Stress: Neurobiology and Neuroendocrinology

Edited by Marvin R. Brown, George F. Koob, and Catherine Rivier

New York, Marcel Dekker, Inc., 1991. 703 pp.

Stress: Neurobiology and Neuroendocrinology is an ambitious attempt to review the latest work in stress research to, state the editors, stimulate “… the development of innovative methods … for further studies in stress biology.” The work presents a great deal of data on stress biology, endocrinology, and physiology, and is for the most part a well-written and fully referenced contribution to the field of stress research.

The book, a collection of 29 reviews by biomedical faculty at American institutions, is organized into four main sections: (1) a general overview regarding issues defining and measuring stress; (2) basic central nervous system (CNS) and endocrine biology during stress; (3) discussions of pathophysiology resulting from stress, such as ischemia, gastric ulcers, immune dysfunctions, and psychiatric disorders; and (4) stress management strategies with explanations of how they may work.

Section three, which concerns itself with stress pathophysiology, is perhaps the book’s strongest section. Here the authors effectively demonstrate links between stressful events and eventual disease processes and provide critical reviews of their fields. For example, Chapter 3 tackles the role of mental stress in causing myocardial ischemia. The authors persuasively argue for ischemia as the best measurement of cardiac pathology vis-a-vis stress, and reproduce studies of ischemia during mental stress over an array of diagnostic modalities (technetium, echocardiography, PET). They further proceed to explain the possible endothelial pathophysiology in response to acetylcholine, resulting in coronary vasoconstriction and subsequent ischemia. In their summary, the authors lucidly delineate avenues of further research.

Chapter 27 reviews stress-induced immune dysfunction in humans. In this chapter, the author ably points out the gap in current research: although studies exist which show an association between psychological stress and immune changes, and psychological stress and disease, there exists a dearth of studies to demonstrate a clear association among all three. He questions the current assumption of the role of endogenous cortisol in immunosuppression by showing studies in which elevated cortisol during stressful events did not always result in depressed natural killer cell activity. Laudably, the author does not leave the reader to wonder about other mechanisms of immune suppression and presents studies which demonstrate that the autonomic nervous system may be ultimately responsible.

The book’s major missed opportunity is a cohesive chapter which connects the disparate discussions of neurobiology and pathophysiology. Chapter 2, the closest stab at this goal, is clearly written, yet digresses into dozens of areas. Instead, a lucid summary of the basic science chapters which follow, demonstrating stress as an insult to the CNS and the endocrine system, which filters down to other organ systems, would have been highly valuable. Aside from suggestive studies, however, this chapter does not include sufficient evidence to support such a theory. Chapter 29 on “Stress Technology Medicine,” another chapter which could demonstrate how various systems interact with one another, spends much of its force explaining the theory of autonomic rhythms and laterality (supported by a collection of one-subject experiments). It leaves the reader disappointed, stating that “the credibility of these sophisticated tools” (fascinating yogi relaxation techniques combining breathing and body position) “comes best through their application” without showing any studies demonstrating stress-reducing effects of these relaxation techniques.

In summary, this book is, for the most part, a well-organized contribution to the field of stress research in its cataloging of the latest findings in one accessible work. Unarguably, much of this information is not easily obtained in the standard medical and scientific texts. This volume can be especially helpful to investigators, working with one particular area of stress biology and physiology, who wish to obtain rapid knowledge of other related fields. It may also be of use to physicians and to health personnel who have a strong desire to grasp the complex science underlying stress and its influence on disease. In many ways, such a work may represent one praiseworthy attempt to gather together the current knowledge of mind’s effects and relate it to disparate organ dysfunctions. Yet it is perhaps too much to ask this work to make durable connections between the different research areas and to allow the reader “a look beyond the trees.” More to the point, that flaw may be a reflection on this still unmapped and intertwined field of neurobiology and pathophysiology, and further editions on the subject will no doubt strive to achieve just such a goal.

Stress, the Aging Brain, and the Mechanisms of Neuron Death

Stress, the Aging Brain, and the Mechanisms of Neuron Death

Robert M. Sapolsky

Cambridge, M., The MIT Press, 1992.429 pp

Does stress kill brain cells, and if so, how? In Stress, The Aging Brain, and Mechanisms of Neuronal Death, Dr. Robert Sapolsky presents data supporting the disturbing notion that psychological stresses may be associated with chemical processes in the brain that subject neurons to toxic processes. Dr. Sapolsky’s research, which has taken him from the African veldt to the neurobiology laboratory, provides a framework to orient readers to this interesting review.

In a well-crafted presentation, Dr. Sapolsky integrates his highly original research with related topics of great interest to neuroscientists, neurologists and psychiatrists. He takes care to review hot issues, such as the impact of glucocorticoids on brain function, the role of N-methyl-D-aspartate (NMDA) receptors in learning and neurotoxicity, and the function of nitric oxide as a mediator of NMDA receptor function. In a particularly creative step, Dr. Sapolsky bridges the traditional neuropharmacologic focus on neuro-modulation and the study of energy regulation within neurons during neuromodulation. He presents evidence to support the hypothesis that elevated glucocorticoid levels associated with stress deplete neuronal energy, making them less capable of fending off the toxic effects of inotropic excitatory amino acid receptor stimulation and its associated increase in calcium influx.

As the product of four years of work and “everything (he) knows as of January 10, 1992,” this book contains a prodigious amount of information presented in a thoughtful and user-friendly fashion. It is evident that Dr. Sapolsky has considered challenges facing the reader. Each chapter begins with a review of the book to that point and finishes with a summary of concepts presented within the chapter. These efforts make the text more accessible and enhance its utility as a reference source. In a scientific world dominated by least publishable units and multi-authored texts, Dr. Sapolsky succeeds in developing his views on stress and neurotoxicity in depth with an informal and somewhat socratic style. This stylistic approach makes the large body of information presented more engaging to the reader.

Dr. Sapolsky acknowledges the limitations of his book, occasionally, as they appear in the text. He reviews rapidly evolving fields of research. As a result, significant developments have already occurred in some areas of study reviewed in this book. Also, clinical perspectives on the type of stresses that push neurons “to the brink” could be developed further. The notion that routine social stresses might increase neuronal loss during a seizure is less formidable than the hypothesis that these stresses are neurotoxic in the absence of a medical crisis. One might also have appreciated a more thorough discussion of psychological trauma and its aftermath.

Overall, this is a very good book for researchers in many areas of clinical and basic neurosciences. It serves as a good entry point for researchers and clinicians interested in the areas of stress, neuroactive corticosteroids, excitatory amino acids, and neurotoxicity. Researchers well-versed in these areas may benefit from Dr. Sapolsky’s novel evaluations of a broad range of data and the numerous and intriguing hypotheses presented.