EFFECTS OF PLASMA-GLUCOSE MANIPULATIONS ON FOOD-INTAKE IN WHITE-CROWNED SPARROWS

Migratory birds show a number of physiological adaptations for long di stance flight, including increased storage and utilization of fat prom oted by increased food intake before migration. However, the relations hip between food intake and metabolic fuels in migratory birds has rec eived little attention. To determine whether food intake is sensitive to carbohydrate utilization in white-crowned sparrows (Zonotrichia leu cophrys gambelii) maintained on short days (9L, 15D), we manipulated p lasma glucose levels by injecting insulin (0.5, 1, 2, 4 U/kg, intramus cular) and glucagon (1, 10, 25, 50 mu g/kg, intraperitoneal) and measu red the feeding response. Low doses of insulin (0.5 or 1 U/kg) did not affect feeding and higher doses (2 and 4 U/kg) significantly decrease d food intake after 30, 60 and 120 min. Similarly, the highest glucago n doses (25 and 50 mu g/kg) significantly decreased feeding. While ins ulin significantly decreased plasma glucose concentrations dose-depend ently, glucagon caused a significant and dose-dependent increase in gl ucose levels. Injections of glucose (10, 50, 100 mg/kg, intraperitonea l) had no significant effect on food intake. These results suggest tha t food intake in white-crowned sparrows is not sensitive to changes in plasma glucose levels. (C) 1997 Elsevier Science Inc.