METABOLIC INTEGRATION IN LOCUST FLIGHT - THE EFFECT OF OCTOPAMINE ON FRUCTOSE 2,6-BISPHOSPHATE CONTENT OF FLIGHT-MUSCLE IN-VIVO

The biogenic amine octopamine was injected into the haemolymph of 20-days old male locusts, Locusta migratoria, and the content of fructose 2,6-bisphosphate, a potent activator of glycolysis, was measured in the flight muscle after various times. Octopamine brought about a transient increase in fructose 2,6-bisphosphate. After the injection of 10 mu 1 of 10 mmol.l(-1) D, L-octopamine fructose 2,6-bisphosphate was increased by 61% within 2 min. Ten minutes after the injection fructose 2,6-bisphosphate was increased to 6.71 +/- 0.89 nmol.g(-1) flight muscle, almost 300% over the control value. Flight caused fructose 2,6-bisphosphate in flight muscle to decrease, but this decrease was counteracted by octopamine injected into the haemolymph of flying locusts. Octopamine and fructose 2,6-bisphosphate may act as signals to stimulate the oxidation of carbohydrate and to integrate muscle performance and metabolism. This mechanism appears particularly significant in the initial stage of flight when carbohydrates are the main fuel.