Serotonergic Innervation of the Salivary Glands and Central Nervous System of AdultGlossina pallidipesAusten (Diptera: Glossinidae), and the Impact of the Salivary Gland Hypertrophy Virus (GpSGHV) on the Host

Abstract

Using a serotonin antibody and confocal microscopy, this study reports for the first time direct serotonergic innervation of the muscle sheath covering the secretory region of the salivary glands of adult tsetse fly, Glossina pallidipes Austen. Reports to date, however, note that up until this finding, dipteran species previously studied lack a muscle sheath covering of the secretory region of the salivary glands. Direct innervation of the salivary gland muscle sheath of tsetse would facilitate rapid deployment of saliva into the host, thus delaying a host response. Our results also suggest that the neuronal and abnormal pattern seen in viral infected glands by the Glossina pallidipes salivary gland hypertrophy virus (GpSGHV) is due to a compensatory increased branching of the neurons of the salivary glands, which is associated with the increased size of the salivary glands in viral infected flies. This study shows for the first time serotonin in the cell bodies of the brain and thoracico-abdominal ganglion in adult tsetse, G. pallidipes Austen (Diptera: Glossinidae). A hypothesis is proposed as to whether innervation of the muscle sheath covering of the secretory region of the salivary glands is present in brachyceran compared with nematoceran dipterans; and, a plea is made that more research is needed to develop a blood feeding model, similar to that in the blow flies, for elucidating the various mechanisms involved in production and deployment of saliva.

Neuro-Olfactory Regulation and Salivary Actions: A Coordinated Event for Successful Blood-Feeding Behavior of Mosquitoes

“…The simultaneous induction of two different pathways leads to the activation of either phospholipase C (PLC)/inositol 1,4,5-trisphosphate (IP3)/diacylglycerol/ Ca 2+ signaling pathway or cyclic AMP/adenylyl cyclase signaling cascade which are the potent secondary messengers found to play a significant role in insect salivation [107,108]. Studies in blood-feeding insects are limited to Aedes aegypti mosquito and on tsetse flies Glossina pallidipes, depicting the presence of serotonergic innervation in their salivary glands [109,110]. Together it can be stated that both the biogenic amines and neuropeptides play a crucial role in insect salivation by modulating the salivary glands' ability to alter second messenger level and ion channel conformation.…”