Meeting Abstract

18.6  Tuesday, Jan. 4  Neuroendocrine Regulation of Food Intake During Acute Stress in the Tilapia, Oreochromis mossambicus UPTON, K. R.*; RILEY, L. G.; Univ. of California, Fresno kelliupton@mail.fresnostate.edu

Fish encounter a number of environmental stressors, including variable water quality, temperature, and food availability. The stress response that ensues is orchestrated by the sympathetic nervous system as well the hypothalamic-pituitary-interrenal axis, principally resulting in the release of cortisol. These two mechanisms share the overall effect of mobilizing metabolic energy and redirecting it towards homeostatic maintenance. Consequently, an important factor altered by stress in fish is reduced food intake. We have previously shown reduced food intake in response to an acute stress in tilapia, which seems to be regulated in part by an accompanying decrease in mRNA levels of the orexigenic factors neuropeptide Y and ghrelin within the hypothalamus, the primary appetite regulation center. However, whether cortisol is mediating these effects is unknown. Therefore, the current study investigates the effects of metyrapone, a cortisol synthesis inhibitor, on food intake during an acute stress. Metyrapone was administered via feed in three experimental groups receiving doses of 10, 25, and 50mg/kg body weight for 1 wk prior to a 30 min crowding and handling stress. Following the stressor, fish were allowed to feed for 1 h. Stress significantly (P < 0.01) reduced food intake. Additionally, metyrapone treatment dose-dependently blocked the stress-induced reduction in food intake, with the 25 and 50 mg/kg doses significantly (P < 0.05 and 0.001, respectively) reversing the effect of stress on food intake. These results suggest that cortisol mediates the observed reduction in food intake in tilapia. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2010-65206-20615 from the USDA National Institute of Food and Agriculture to LGR.