Neurophysiological and behavioral aspects of the mosquito Aedes aegypti in the taste perception to ATP as phagostimulant and its effect on different taste qualities.

Mosquitoes are insects’ vector responsible for the transmission of parasitic and viral diseases to millions of people worldwide. Understanding physiological processes like gustation and mosquito’s behavior is important for disease surveillance and for designing and implementing effective measures for disease control and prevention. Gustatory stimuli are perceived by cells on mouthparts and legs of mosquitoes. Identifying and classifying active feeding stimulants and their specific chemoreceptor cells, in the labellar and cibarial sensilla, allowed us to construct a correlation between the selective activation and the behavioral responses of these important vectors of diseases.

In this thesis, I performed systematic electrophysiological recordings, which measured the neurophysiological responses of the receptors cells to stimuli and quantified their responses. Hence, the identification of the most active chemo-stimulants including water, sugars, some nucleotides, and their interaction, so deciphering biological taste perception processes. Moreover, behavioral tests, such as feeding through silicone membranes with warm solutions, were directly related with electrophysiological enhanced or inhibited responses, according to specific phagostimulants and inhibitors respectively tested.

With the main purpose to investigate the taste perception of A. aegypti to purines, which are the most primitive and prevalent chemical messengers in the animal and plant kingdoms (Burnstock and Verkhratsky 2009), we evaluated the electrophysiological and behavioral responses to nucleotides. The response evaluation to a single taste quality where ATP is representing the umami taste and mixed with other canonical tastes, such as sweet and salty, allow us to extend our knowledge on the purinergic signaling in this mosquito specie. We found a novel pharmacological profile to elicit gorging responses in saline solutions, concluding that a mix of P2X7 and a P2X4 are controlling this behavior. Furthermore, in labellar sensilla, we proposed that a P2Y is implicated in the perception of nucleotides. Also, behavioral results revealed a synergistic response between sweet and umami taste qualities, strongly enhancing the engorged state of starved mosquitoes. Lastly, we evaluated the importance of chemical and physical factors, of a given physiological solution during the gorging behavior, to finally propose a novel solution less salt saturated and slightly below the osmotic pressure of blood, which can be used to evaluate the response to phagostimulants such as ATP or to characterize other receptors still not described.

Keywords: Aedes aegypti, electrophysiology, gorging responses, phagostimulants, taste cells, gustatory receptors, pharmacological profile, taste qualities, sugars, ATP, water, osmotic pressure.