Distribution of serotonin in the central nervous system of the blood-feeding heteropteran, Triatoma infestans (Heteroptera: Reduviidae).

Abstract

The distribution of serotonin was studied in the Triatoma infestans central nervous system by using immunocytochemistry. Serotonin immunoreactive cell bodies and fibers were observed in the brain, subesophageal ganglion, and thoracic ganglia. In the brain, serotonin-like immunoreactivity was detected in a limited number of somata, which gave rise to an extensive network of labeled neurites in patterned as well as in nonglomerular neuropils. Immunolabeled perikarya were observed in the optic lobe and in the anteromedial and caudolateral soma rinds of the protocerebrum. Deutocerebral immunoreactive somata were mainly found in the medial layer surrounding the antennal lobe glomeruli, as well as in relationship to the antennal mechanosensory and motor center. The subesophageal ganglion contained serotonin immunoreactive perikarya of variable sizes and moderate to low density of positive fibers. In the prothoracic ganglion, immunoreactive somata were detected near the cephalic connectives as well as in its caudal end. Serotonin immunoreactive somata and fibers were observed in the posterior ganglion of the thorax, with the abdominal neuromeres harboring the highest number of immunolabeled perikarya. These results show that there is a widespread unique serotonergic system in the CNS of Triatoma infestans and suggest that the indolamine could act as a neuromodulator or as a neurohormone.