Multiple forms of cerebral peptides with steroidogenic functions in pupal and adult brains of the yellow fever mosquito, Aedes aegypti.

In the adult mosquito, Aedes aegypti, the cerebral egg development neurosecretory hormone (EDNH) regulates reproduction by activating the ovaries to synthesize the steroid hormone ecdysone, while during postembryonic development the cerebral prothoracicotropic hormone (PTTH) activates the prothoracic glands to synthesize ecdysone. In each case, ecdysone than drives stage-specific physiological processes. Since EDNH and PTTH share a common steroidogenic function, it is conceivable that they are similar, if not the same, peptide(s). This investigation has begun to address this possibility by determining structural and functional relationships between these two families of neuropeptides. The peptides having EDNH activity in adult and pupal heads of Aedes aegypti were characterized on the basis of their molecular weights and their biological properties in in vitro and in vivo bioassays for EDNH. Gel filtration chromatography of extracts revealed fractions with EDNH activity having molecular weights of approximately 11 kDa and approximately 24 kDa. The similarities in the functional dynamics of these two activities in the different bioassays suggested that comparable moieties existed in pupal and adult brains. The sensitivity of these moieties to proteolytic hydrolysis indicated that they were proteins. Thus at least two EDNH-like peptides appear to be present in pupal and adult heads of Aedes aegypti. The apparent existence of more than one molecular weight form of EDNH has not been reported previously. Since these moieties are present in both pupal and adult heads, it is possible that they have the same steroidogenic function in the two different stages, i.e., to activate ecdysone synthesis, by prothoracic glands in larvae and pupae and by the ovaries in adults.