Human central diabetes insipidus (CDI) is a neurobiological syndrome characterized by the presence of hypotonic polyuria, hypernatremia, and polydipsia. CDI can be acquired (aCDI) as the result of brain damage to magnocellular neurosecretory cells or fibers that constitute the hypothalamic-neurohypophyseal system or can be caused by genetic disorders (hereditary CDI). aCDI can be experimentally induced by various surgical interventions, including neurohypophysectomy, pituitary stalk compression (PSC), hypophysectomy, and hypothalamic mediobasal lesions. CDI has been associated with a deficient production of arginine vasopressin (AVP) (the antidiuretic hormone secreted by magnocellular system), while more recently, aCDI animal studies also suggest the possible involvement of oxytocin (OT) (a natriuretic-promoting hormone secreted by neurosecretory systems) and other factors related to serum fluid concentration. Both humans and animals with aCDI may benefit from the combined administration of AVP and OT and, importantly, from a low-sodium diet. Moreover, increased OT levels are observed in Brattleboro rats (with mutated AVP gene), which may explain the regulatory hydromineral capacity shown by these animals after hydromineral challenges. In short, the symptoms shown by the different CDI animal models suggest the involvement of additional factors besides the absence of AVP, which appear to depend on the particular neurobiological systems affected in each case.
Part of the book: Experimental Animal Models of Human Diseases
Enteral nutrition is often mandatory, especially for patients in vegetative or minimally conscious state. However, its application is nonviable in certain cases due to various adverse effects. Some of these are explained by absence of the cephalic phase of digestion, during which exocrine, endocrine, and motor physiological responses prepare the digestive system to receive, digest, transform, and utilize ingested nutrients. These responses result from the stimulation by nutrients of cephalic sensory systems, mainly in the oropharyngeal cavity, and can also be elicited by food-related thoughts or expectations. The digestive system appears able to rapidly assess the suitability of food and transmit this information to the brain. The vagus nerve and its brainstem relays in the caudal nucleus of the solitary tract (NST) and parabrachial complex appear to participate in the anatomic pathway responsible for this rapid processing. Thus, blockade of the vagus nerve, NST, or external lateral parabrachial region (LPBe) interrupts expression of conditioned taste preferences induced by administration of “predigested” food, while LPBe activation by electric stimulation generates similar preferences to those observed after cephalic food administration. This review may help design enteral diets better adapted to digestive physiology and develop pharmacological interventions against adverse effects of enteral nutrition.
Part of the book: Feed Your Mind