5-HYDROXYTRYPTAMINE IN THE SALIVARY-GLANDS OF ADULT FEMALE AEDES-AEGYPTI AND ITS ROLE LN REGULATION OF SALIVATION

A dense plexus of axons, immunoreactive to antisera against 5-hydroxyt ryptamine (5-HT, serotonin) and surrounding the proximal medial lobe o f the salivary gland of adult female Aedes aegypti mosquitoes, was dem onstrated by means of whole-mount fluorescence immunocytochemistry. Th is innervation originates in the stomatogastric nervous system. 5-HT-i mmunoreactive innervation is absent in male salivary glands, suggestin g that 5-HT is involved in blood-feeding, Furthermore, female mosquito es treated with the 5-HT-depleting agent alpha-methyltryptophan (AMTP) and then allowed to feed on a rat exhibited a significantly longer me an probing period and a lower blood-feeding success rate than did cont rol mosquitoes, When female mosquitoes were experimentally induced to salivate into mineral oil, AMTP-treated individuals secreted significa ntly less saliva than did control mosquitoes, These samples of saliva also contained significantly lower concentrations of apyrase, an enzym e important in blood-feeding, Injection of 5-HT into both AMTP-treated and control mosquitoes elicited significant increases in the volume o f secreted saliva and/or its apyrase content, We conclude that 5-HT pl ays an important role in the control of salivation in adult female A. aegypti.