Dynamics of release and activity of select neuropeptides post-bloodmeal in the female mosquito, Aedes aegypti.

Female Aedes aegypti secrete urine rapidly post-bloodmeal ingestion, with diuresis beginning immediately for removal of excess salts and water. This post-prandial diuresis includes a peak, post-peak and late phase, involving the combined actions of multiple hormones, including diuretic and anti-diuretic factors. Calcitonin-like diuretic hormone 31 (DH31) and kinin peptides stimulate diuresis through actions on their cognate receptors localized in the Malpighian 'renal' tubules (MTs). In contrast, the anti-diuretic neurohormone CAPA inhibits secretion by MTs stimulated by select diuretic hormones, including DH31. Although DH31 and kinin are critical in achieving post-prandial diuresis, and CAPA functions as an important anti-diuretic hormone, the kinetics of their release and haemolymph levels remain unknown. Here, using heterologously expressed receptors for A. aegypti DH31, CAPA and kinin, we investigated the titres of these hormones in the haemolymph of female mosquitoes at different time points after blood feeding. Haemolymph extracts from female mosquitoes contained levels of diuretic peptides, specifically kinin and DH31, that increased immediately post-bloodmeal, with levels peaking at 2 and 5 min, respectively, whereas DH31 levels remained elevated for 15 min. Comparatively, levels of CAPA peptides in the haemolymph steadily increased 15 min post-blood feeding, with levels peaking at 30 min. Synergistic actions were observed between DH31 and a kinin-like peptides on the MTs, providing a physiological context for the rapid release of these peptides into the female haemolymph. Altogether, these results demonstrate that DH31 and kinin are released immediately post-bloodmeal and, along with CAPA peptides, have a coordinative action on the MTs to maintain haemolymph homeostasis through regulation of primary urine secretion.