" THE MAIN OBJECTIVE OF THE PROPOSAL IS TO OBTAIN INFORMATION ON SOME OF THE PHYSIOLOGICAL MECHANISMS INVOLVED IN THE REGULATION OF FEEDING IN FISH AND TO KNOW HOW SEVERAL FACTORS RELATED TO AQUACULTURE PRODUCTION ALTERING WELFARE CAN INTERFERE WITH THEM, AND THEREFORE ALTER FOOD INTAKE. WE AIM TO CONTINUE THE STUDIES CONDUCTED TO DATE BY THE RESEARCH GROUP THAT ALLOWED TO CONTRIBUTE TO THE SCIENTIFIC BASIS OF THE IMPACT OF NUTRIENT SENSING SYSTEMS, THE CIRCADIAN SYSTEM, AND STRESS SIGNALS ON THE INTEGRATED RESPONSE OF FOOD INTAKE IN FISH. SPECIFICALLY, USING RAINBOW TROUT AND SOLE AS EXPERIMENTAL MODELS, THE EXPECTED RESULTS OF THIS PROJECT WILL SERVE TO CLARIFY HOW THE METABOLIC INFORMATION OBTAINED FROM THE NUTRIENT LEVELS IN THE DIET, THROUGH GLUCOSENSOR AND FATTY ACID SENSOR SYSTEMS, MODULATES FOOD INTAKE, AND HOW THESE MECHANISMS ARE ALTERED IN STRESSFUL SITUATIONS. IN GLUCOSE SENSORS SYSTEMS, OUR OBJECTIVE IN RAINBOW TROUT IS TO CHARACTERIZE THE SPECIFIC LOCATION OF THE SENSOR SYSTEMS MEDIATED BY GLUCOKINASE AT THE NEURONAL LEVEL, AS WELL AS TO DEMONSTRATE THE PRESENCE OF SYSTEMS ALTERNATIVE TO THAT MEDIATED BY GLUCOKINASE. IN SOLE, SPECIES MORE TOLERANT TO GLUCOSE, WE WILL ASSESS THE INVOLVEMENT OF GLUCOSENSING SYSTEMS IN THE CONTROL OF FOOD INTAKE. IN FATTY ACID SENSOR SYSTEMS, WE WILL CHARACTERIZE IN RAINBOW TROUT THEIR FUNCTIONALITY BASED ON THEIR RESPONSES TO DECREASES IN CIRCULATING LEVELS OF FATTY ACIDS, THEIR RESPONSE IN ANIMALS FED DIETS WITH DIFFERENT LIPID CONTENT, ITS ENDOCRINE MODULATION, AND THE CHARACTERIZATION OF THE MOLECULAR MECHANISMS THAT RELATE THEM TO FOOD INTAKE. WE WILL ALSO ASSESS HOW THE INTEGRATION OF THE METABOLIC INFORMATION CHANGED UNDER STRESS CONDITIONS, AND WE WILL OBTAIN EVIDENCE ABOUT THE INTEGRATIVE RESPONSE TO CHANGES IN THE LEVELS OF MORE THAN ONE NUTRIENT. FURTHERMORE, USING AS A MODEL THE RAINBOW TROUT, THE PROJECT WILL BE FOCUSED ON THE UNDERLYING MOLECULAR MACHINERY BEHIND PHYSIOLOGICAL RHYTHMS IN FISH. IN PARTICULAR, WE WILL ASSESS THE EXPRESSION OF SO-CALLED CLOCK GENES (MOLECULAR MECHANISM OF THE CIRCADIAN SYSTEM) IN THE LIVER, AND THE INFLUENCE ON THESE RHYTHMS OF FACTORS RELATED TO FOOD INTAKE AND DIFFERENT STRESS CONDITIONS. AT CEREBRAL LEVEL, WE WILL EVALUATE IN DIFFERENT REGIONS THE CYCLIC EXPRESSION OF CIRCADIAN GENES AND ITS MODULATION BY FOOD INTAKE TO DEFINE THE BRAIN AREAS WHERE THE INFORMATION FROM FEEDING DETERMINES RHYTHMIC RESPONSES OF THE FISH. MOREOVER, WE WILL ESTABLISH A RELATIONSHIP OF THE CIRCADIAN SYSTEM WITH MONOAMINERGIC AND PEPTIDERGIC NEUROTRANSMITTERS INVOLVED IN THE REGULATION OF FOOD INTAKE. SEVERAL HORMONES (MELATONIN, CORTISOL) CAN CONTRIBUTE TO THE ADJUSTMENT OF CIRCADIAN ACTIVITY AT BOTH PERIPHERAL AND CEREBRAL LEVEL, AND THEREFORE THEIR ROLE WILL BE ASSESSED IN DETAIL. FINALLY, WE ALSO AIM TO ELUCIDATE THE ROLE OF THE SEROTONERGIC SYSTEM IN THE BEGINNING OF THE STRESS RESPONSE AND IN THE RECOGNITION OF STRESSFUL STIMULI BY THE FISH, FOR WHICH WE WILL EVALUATE DIFFERENT STRESSFUL CONDITIONS IN RAINBOW TROUT AND SOLE."