EFFECTS OF 5,7-DHT UPON FEEDING AND SEROTONIN CONTENT OF VARIOUS TISSUES IN RHODNIUS-PROLIXUS

In Rhodnius prolixus there are extensive central and peripheral serotonergic systems. Injection of 5,7-dihydroxytryptamine (5,7-DHT) caused a notable decrease in the staining intensity of serotonin-like immunofluorescent processes on the salivary gland ducts and abdominal nerves, coupled with an enhancement in the staining intensity of serotonin-like immunoreactive dorsal, unpaired, median neurones in the mesothoracic ganglionic mass. Quantification of serotonin using HPLC confirmed that 5,7-DHT injection caused a severe decrease in the serotonin content of the salivary glands and abdominal verves, but did not reduce the overall serotonin content of the various ganglia of the central nervous system. Rhodnius injected with 5,7-DHT ingested a blood meal that was significantly smaller than that of control bugs, and in addition, did not appear to undergo cuticle plasticization. These results demonstrate that 5,7-DHT is an effective neurotoxin of peripheral serotonergic stores in this insect. Furthermore, the effects of 5,7-DHT are consistent with the idea that serotonin is integrally involved in the feeding activities of R. prolixus. © 1990.