IMMUNOHISTOLOGICAL LOCALIZATION OF REGULATORY PEPTIDES IN THE MIDGUT OF THE FEMALE MOSQUITO AEDES-AEGYPTI

The midgut of the female mosquito Aedes aegypti was studied immunohist ologically with antisera to various regulatory peptides. Endocrine cel ls immunoreactive with antisera to perisulfakinin, RFamide, bovine pan creatic polypeptide, urotensin 1, locustatachykinin 2 and allatostatin s A1 and B2 were found in the midgut. Perisulfakinin, RFamide and bovi ne pancreatic polypeptide all react with the same, about 500 endocrine cells, which were evenly distributed throughout the posterior midgut, with the exception of its most frontal and caudal regions. In additio n, these antisera recognized three to five neurons in each ingluvial g anglion and their axons, which ran longitudinally over the anterior mi dgut, as well as axons innervating the pyloric sphincter. The latter a xons appear to be derived from neurons located in the abdominal gangli a. Antisera to two different allatostatins recognized about 70 endocri ne cells in the most caudal area of the posterior midgut and axons in the anterior midgut whose cell bodies were probably located in either the brain or the frontal ganglion. Antiserum to locustatachykinin 2 re cognized endocrine cells present in the anterior midgut and the most f rontal part of the posterior midgut, as well as about 50 cells in the most caudal region of the posterior midgut. Urotensin 1 immunoreactivi ty was found in endocrine cells in the same region as the perisulfakin in-immunoreactive cells, but no urotensin-immunoreactive axons were fo und in the midgut. Double labeling experiments showed that the urotens in and perisulfakinin immunoreactivities were located in different cel ls. Such experiments also showed that the locustatachykinin and allato statin immunoreactivities in the most caudal area of the posterior mid gut were present in different cells. No immunoreactivity was found in the mosquito midgut when using antisera to corazonin, allatotropin or leucokinin IV. Since these peptides have either been isolated from, or can reasonably be expected to be present in mosquitoes, it was conclu ded that these peptides are not present in the mosquito midgut.