Behavioral Neuroscience, Neuropsychology and Physiological Psychology, Pharmacology, Endocrine and Autonomic Systems
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Scopus Publications
Scopus Publications
Sodium Homeostasis, a Balance Necessary for Life Antonio Bernal, María A. Zafra, María J. Simón, Javier Mahía Nutrients, 2023 Body sodium (Na) levels must be maintained within a narrow range for the correct functioning of the organism (Na homeostasis). Na disorders include not only elevated levels of this solute (hypernatremia), as in diabetes insipidus, but also reduced levels (hyponatremia), as in cerebral salt wasting syndrome. The balance in body Na levels therefore requires a delicate equilibrium to be maintained between the ingestion and excretion of Na. Salt (NaCl) intake is processed by receptors in the tongue and digestive system, which transmit the information to the nucleus of the solitary tract via a neural pathway (chorda tympani/vagus nerves) and to circumventricular organs, including the subfornical organ and area postrema, via a humoral pathway (blood/cerebrospinal fluid). Circuits are formed that stimulate or inhibit homeostatic Na intake involving participation of the parabrachial nucleus, pre-locus coeruleus, medial tuberomammillary nuclei, median eminence, paraventricular and supraoptic nuclei, and other structures with reward properties such as the bed nucleus of the stria terminalis, central amygdala, and ventral tegmental area. Finally, the kidney uses neural signals (e.g., renal sympathetic nerves) and vascular (e.g., renal perfusion pressure) and humoral (e.g., renin–angiotensin–aldosterone system, cardiac natriuretic peptides, antidiuretic hormone, and oxytocin) factors to promote Na excretion or retention and thereby maintain extracellular fluid volume. All these intake and excretion processes are modulated by chemical messengers, many of which (e.g., aldosterone, angiotensin II, and oxytocin) have effects that are coordinated at peripheral and central level to ensure Na homeostasis.
Differential rewarding effects of electrical stimulation of the lateral hypothalamus and parabrachial complex: Functional characterization and the relevance of opioid systems and dopamine Maria J Simon, Maria A Zafra, Amadeo Puerto Journal of Psychopharmacology, 2019 Background: Since the discovery of rewarding intracranial self-stimulation by Olds and Milner, extensive data have been published on the biological basis of reward. Although participation of the mesolimbic dopaminergic system is well documented, its precise role has not been fully elucidated, and some authors have proposed the involvement of other neural systems in processing specific aspects of reinforced behaviour. Aims and methods: We reviewed published data, including our own findings, on the rewarding effects induced by electrical stimulation of the lateral hypothalamus (LH) and of the external lateral parabrachial area (LPBe) – a brainstem region involved in processing the rewarding properties of natural and artificial substances – and compared its functional characteristics as observed in operant and non-operant behavioural procedures. Results: Brain circuits involved in the induction of preferences for stimuli associated with electrical stimulation of the LBPe appear to functionally and neurochemically differ from those activated by electrical stimulation of the LH. Interpretation: We discuss the possible involvement of the LPBe in processing emotional-affective aspects of the brain reward system.
Increased short-term food intake after external lateral parabrachial subnucleus lesions in rats Antonio D R Agüera, M. A. Zafra, F. Molina, A. Puerto Acta Neurobiologiae Experimentalis, 2019 The vagus nerve and several brainstem nuclei to which it projects have been closely associated with food intake. The aim of this study was to determine the degree to which the same or different information on food intake is processed by this nerve and by one of these nuclei, the external lateral parabrachial subnucleus (LPbNe). For this purpose, we analyzed the solid and liquid food intake of Wistar rats subjected to vagal deafferentation with capsaicin or lesions of the LPbNe. Vagotomized animals consumed significantly larger amounts of solid food during the first 24 h post‑surgery but not at 48, 72, or 96 h. Animals with LPbNe lesions also consumed larger amounts of liquid and solid foods but only during periods of 60 min on day 5 and 90 min on day 6 post‑surgery, respectively. According to these findings, both the vagus nerve and the LPbNe appear to be involved in short‑term regulation of food intake, although they participate over different time scales. These data are discussed in terms of the potential importance of the vagal‑parabrachial axis in the rapid processing of nutritional information from the upper gastrointestinal tract.
Chemical afferent vagal axotomy blocks re-intake after partial withdrawal of gastric food contents María A. Zafra, Filomena Molina, Amadeo Puerto Nutritional Neuroscience, 2017 Objectives: The aim of this study was to investigate the biological process by which animals regulate meal size. An experimental procedure for its study is to examine food re-intake after partial withdrawal of gastric food contents. Methods: The aim of the present experiments was to investigate the role of vagal afferents in food re-intake after perivagal administration of capsaicin, a neurotoxin that specifically damages weakly myelinated or unmyelinated vagal sensory axons. Results: In experiment 1, capsaicin-treated animals initially consumed higher amounts of food in comparison to controls (in first 24 hours) but their excess intake was compensated for in subsequent daily satiation tests. However, capsaicin treatment impaired the common short-term re-intake behavior observed in control rats after partial removal of gastric food nutrients, and the lesioned animals consumed significantly less food than had been withdrawn after completion of the initial meal; moreover, in this deficit condition, no counteraction was observed in subsequent repeated tests. This behavioral disturbance cannot be attributed to an indirect effect of capsaicin on gastric emptying volume, because the stomach contents were similar in both groups (Experiment 2). Discussion: These findings are discussed in terms of the critical role played by vagal afferents in rapid visceral adjustments related to short-term food intake, as also observed in other gastrointestinal regulatory behaviors that require immediate processing of visceral sensory information.
Learned flavor preferences induced by intragastric administration of rewarding nutrients: Role of capsaicin-sensitive vagal afferent fibers Maria A. Zafra, Filomena Molina, Amadeo Puerto American Journal of Physiology Regulatory Integrative and Comparative Physiology, 2007 Learned flavor preferences can be established after intragastric nutrient administration by two different behavioral procedures, concurrent and sequential. In a concurrent procedure, two flavored stimuli are offered separately but at the same time on a daily basis: one stimulus is paired with the simultaneous intragastric administration of partially digested food and the other with physiological saline. In sequential learning, the two stimuli are presented during alternate sessions. Neural mechanisms underlying these learning modalities have yet to be fully elucidated. The aim of this study was to examine the role of vagal afferent fibers in the visceral processing of rewarding nutrients during concurrent ( experiment 1) and sequential ( experiment 2) flavor preference learning in Wistar rats. For this purpose, capsaicin, a neurotoxin that destroys slightly myelinated or unmyelinated sensory axons, was applied to the subdiaphragmatic region of the esophagus to selectively damage most of the vagal afferent pathways that originate in the gastrointestinal system. Results showed that capsaicin [1 mg of capsaicin dissolved in 1 ml of vehicle (10% Tween 80 in oil)] blocked acquisition of concurrent but not sequential flavor preference learning. These results are interpreted in terms of a dual neurobiological system involved in processing the rewarding effects of intragastrically administered nutrients. The vagus nerve, specifically capsaicin-sensitive vagal afferent fibers, would only be essential in concurrent flavor preference learning, which requires rapid processing of visceral information.
