Schematic diagram summarizing diuretic and anti-diuretic control of A Schematic diagram summarizing diuretic and anti-diuretic control of A. aegypti adult MTs. The principal cells are responsible for transport of Na+ and K+ via secondary active transport. Schematic diagram summarizing diuretic and anti-diuretic control of A. aegypti adult MTs. The principal cells are responsible for transport of Na+ and K+ via secondary active transport. The V-type H+-ATPase, localized in the brush border of the apical membrane, produces a H+ gradient that drives the exchange of Na+ and K+ across the apical membrane through cation/H+ antiporters. Ions are secreted from the haemolymph through a Na+:K+:2Cl− cotransporter localized on the basolateral membrane. Neurohormone receptors, including those for 5-HT and the peptides DH31, CRF and CAPA, are localized to the basolateral membrane of principal cells, while the kinin receptor is localized exclusively to stellate cells. Stimulation of MTs with 5-HT and DH31 through their cognate receptors increases levels of the second messenger cAMP. CRF-related peptide receptor activation increases Ca2+ and cAMP depending on the dose of peptide applied, while kinin receptor signalling involves exclusively increases in intracellular levels of Ca2+. Our data indicate an anti-diuretic effect of AedaeCAPA-1 in 5-HT- and DH31-stimulated MTs, inhibiting non-selective cation transport and fluid secretion through an undetermined pathway but, in contrast, having only minor and no inhibitory activity on CRF- and kinin-stimulated diuresis, respectively. This anti-diuretic activity may involve the second messenger cGMP, which duplicates the strong inhibitory effects observed on 5-HT- and DH31-stimulated diuresis acting on principal cells. Lastly, cGMP is also capable of strongly inhibiting kinin-stimulated diuresis that is facilitated via stellate cells, which suggests an additional anti-diuretic factor may exist in mosquitoes. NOS, nitric oxide synthase. Farwa Sajadi et al. J Exp Biol 2018;221:jeb177089 © 2018. Published by The Company of Biologists Ltd