OCTOPAMINE MOBILIZATION OF LIPIDS AND CARBOHYDRATES IN THE HOUSE CRICKET, ACHETA-DOMESTICUS

Injected octopamine elevated both lipids and sugars in the blood of head-ligated adult Acheta domesticus. Head ligation precludes any involvement of peptide hormone release from the corpus cardiacum and eliminates stress induced hyperglycaemia. A 50% increase was the maximal lipaemic response to either octopamine or synthetic cricket adipokinetic hormone, indicating a feedback inhibition. The time course of the lipid response to injected octopamine was shorter than for injection of the cricket's own adipokinetic hormone, which may be related to different receptors. The alpha adrenergic antagonist phentolamine blocked both the lipid and sugar mobilization action of octopamine. For the first time an age-dependent hyperlipaemic response for octopamine is reported, which was very similar to the age-response curve for the cricket's own adipokinetic hormone. A correlation between ovarial development and the sugar and lipid responsiveness to octopamine indicated a functional relationship of octopamine responsiveness to reproduction. A dibutyryl cAMP-induced elevation of both lipids and sugars indicate that cAMP is involved in both sugar and lipid mobilization by octopamine. The phosphorylase a inhibitor flavin mononucleotide inhibited both the lipid and sugar response to octopamine, which implies that phosphorylase a is involved in the octopamine-induced mobilization of both sugar and lipids. The neurotransmitter effectiveness for the hyperlipaemic response was: octopamine > norepinephrine > dopamine > epinephrine.