Sequence, characterization and pharmacological analyses of the adipokinetic hormone receptor in the stick insect, <i>Carausius morosus</i>.

The AKH receptor from stick insects (Phasmatodea) cluster together in one clade distinct from other insect AKHRs, although still similar enough to be an insect AKHR, as opposed to the other GnRH-related receptors of insects, such as ACP and Crz receptors. The phylogenetic analyses support the data obtained from other studies involving receptors for AKH, Crz and ACP peptides. The receptor assay results with AKH analogs corroborated most of the results obtained previously using <i>in vivo</i> studies, thus emphasizing that the endogenous AKHs operate through this receptor to cause hypertrehalosemia in the stick insect. It is also clear that certain residues of the AKH peptides are consistently important in their interaction with the cognate AKH receptor, while other amino acid residues are of different importance to AKH receptors on a broad species- or group-specific manner. The previously observed peculiarity that hypertrehalosemia, in response to AKH injection, is only measurable in stick insects ligated below the head is discussed. No explanations for this, however, can be inferred from the current study.