Neuroscience 1987/22. [antikvár]

IS THE ROLE OF BRAIN ECF [Na] AND HORMONES IN DETERMINATION OF INGESTIVE BEHAVIOUR D.A. Denton, M.J. McKinley, E.G. Tarjan and R.S. Weisinger, Howard Florey Institute of Experimentál Physiology and Medicine, University of Melbourne, Parkville, Australia The progressive growth of knowledge of the brain mechanisms for audit of the state of the milieu interieur has involved recognition of the reactions to body temperature, blood gases, pH, glucose, osmotic pressure and feedback monitoring of hormones, and more recently brain extracellular fluid [Na] in somé species. The phylogenetic emergence of genetically programmed neuronal systems subserving sodium appetite has occurred as maramalian species irradiated over large areas of the planet - the alps and the interior of continents - which have very low Na content of soil and vegetation. Body sodium deficit can occur particularly during the stress of reproduction. Ventricular infusion experiments in sheep and cattle have shown interaction of osmotic pressure and [Na] in determination of thirst. Increase of brain ECF [Na] reduces, and decrease of [Na] greatly stimulates sodium appetite. In sheep recent data on systemic and icv infusions of angiotensin II and converting enzyme inhibitior (CEI), indicate a physiological role for angiotensin II in sodium appetite of- sheep. Lesions of the anterior wall of the third ventricle, which is rich in angiotensin II receptors, causes adipsia in sheep but drinking of hypertonic NaHCO^ solution in response to Na deficiency is unimpaired. The action in sheep or other species of other peptide hormones ACTH, prolactin, oxytocin, and alsó ANF and elodoisin, as weil as the ovarian and adrenal steroids involved in pregnancy, lactation and the response to stress, indicate that the neural systems subserving sodium appetite are pluripotential in their response characteristics. Different selection pressures operated during phylogenesis, the circumstances contriving that either increase or decrease of salt appetite could confer survival advantage. BRAIN CONTROL OF THE INTERNÁL ENVIRONMENT: HYPOTHALAMIC REGULATION OF ADENOHYPOPHYSIAL FUNCTIONS AND ITS IMPLICATIONS Roger Guillemin, The Salk Institute, La Jolla, California, U.S.A It is classical to say that the constancy (homeostasis of Walter Cannon) of the internál environment (le milieu interieur of Claude Bernard) is maintained by both the endocrine system and the nervous system. There is now overwhelming evidence that the brain is the ultimate regulator of both systems, including all classic endocrine functions, through the hypothalamic control of adenohypophysial secretions. This neurohumoral control is exerted by a series of small polypeptides of neuronal origin which have been isolated, characterized and reproduced by totál synthesis, ranging in size from 3 to 44 aminő acid residues. Somé of these neuropeptides are stimulators of pituitary secretions, others are inhibitory for such functions, acting as non competitive antagonists of the agonist ligands. The neurohumoral control of brain origin operates rapidly and can override the slow negative feedback-mechanisms involving reciprocal concentrations of perlpheral hormones and pituitary hormones. Many of the molecules involved in peripheral endocrine functions are alsó found in central neurons. Indeed endocrinology appears more and more as a branch of neuroendocrinology. AGING AND DEMENTIA SYMPOSIUM ABSTRACT R.Katzman, i Normál aging involves relatively minor cognitive changes, e.g., change in processing time and decrease in recent memory; indeed, recent morphometric data indicate that the long held belief that there is a major loss of cortical neurons in normál aging is incorrect. The brain is, however, subject to age-related diseases especially Parkinson's, stroke and Alzheimer's. The incidence of Alzheimer's at age 80 is twenty-fold that at age 60 years. In the United States at age 80 the incidence of Alzheimer's surpasses that of stroke. Three major advances have occurred in regard to Alzheimer's disease: (1) Clinical diagnosis has markedly improved and now approaches 90% accuracy; (2) Understanding of the biology of Alzheimer's has increased with delineation of specific fibrous protein abnormalities and identification of the amyloid precursor gene and the gene linked to familial Alzheimer's, both genes being on chromosome 21; and (3) there have been advances in the correlation of specific nerve cell involvement and neurotransmitter changes with physiological (PET), behavioral and neuropsychological manifestations. NSC 22SUPPL-B