Distribution of FMRFamide-related peptides in the blood-feeding bug, Rhodnius prolixus

Immunohistochemistry was used to study the distribution of FMRFamide-like material in the central and peripheral nervous systems and visceral tissues of 5th instar Rhodnius prolixus. Over 200 immunoreactive cell bodies and their processes as well as extensive neuropile regions were distributed throughout the nervous system. Immunoreactive processes were seen over the cephalic aorta, corpus cardiacum/corpus allatum complex, and in neurohaemal sites on the abdominal nerves. In visceral tissues, immunoreactive processes were seen innervating the salivary glands, the foregut, and the hindgut. Immunoreactive cells were also found in the anterior midgut (i.e., the crop and the anterior intestine). A radioimmunoassay specific for "RFamide" carboxy-terminal peptides was used to quantify the amount and the distribution of FMRFamide-like material. Reversed-phase high performance liquid chromatography of nervous tissue extracts revealed several peaks of immunoreactive material. The results suggest the existence of a number of FMRFamide-related peptides in Rhodnius which may have roles in both central and peripheral transmission, may be released as neurohormones and may have endocrine functions in the gut.