Nitric oxide contributes to high-salt perception in a blood-sucking insect model

Abstract

In all organisms, salts produce either appetitive or aversive responses depending on the concentration. While low-salt concentration in food elicits positive responses to ingest, high-salt triggers aversion. Still the mechanisms involved in this dual behavior have just started to be uncovered in some organisms. In Rhodnius prolixus, using pharmacological and behavioral assays, we demonstrated that upon high-salt detection in food a nitric oxide (NO) dependent cascade is activated. This activation involves a soluble guanylate cyclase (sGC) and the production of cyclic guanosine monophosphate (cGMP). Thus, appetitive responses to low-salt diets turn to aversion whenever this cascade is activated. Conversely, insects feed over aversive high-salt solutions when it is blocked by reducing NO levels or by affecting the sGC activity. The activation of NO/sGC/cGMP cascade commands the avoidance feeding behavior in R. prolixus. Investigations in other insect species should examine the possibility that high-salt aversion is mediated by NO/sSG/cGMP signaling.

Impact of alkaloids in food consumption, metabolism and survival in a blood-sucking insect

“…Based on morphological studies by means of scanning electron microscopy, eight taste sensilla were identified in the anterior part of the pharynx of R. prolixus 36,49 . Likely, these sensilla are responsible for the gustatory evaluation of blood, following biting and sucking a gorge of blood in kissing bugs 36,[56][57][58] . However, electrophysiological studies are necessary to corroborate their function as, for example, bitter-sensitive GRNs tuned to alkaloids.…”

Molecular bases of sensory processes in kissing bugs, vectors of Chagas disease

“…Host skin recognition by taste receptors, as well as that of blood taste properties, has been shown to be relevant for skin piercing and feeding in these bugs [30,31]. The identification of the receptors underlying the molecular bases of NaCl, KCl and ATP recognition, three of the main signals mediating the evaluation of skin and blood quality features, is yet to be revealed.…”

Salty surfaces deter feeding in a blood-sucking disease vector

“…For example, low-salt (< 0.1 M) triggers insect feeding and oviposition, whereas high-salt (> 0.1 M) promotes avoidance and prevents egg-laying (3)(4)(5)(6)(7)(8)(9). Salts are detected by the taste system, a sensory modality that helps animals make predictions about the value of a potential food source, i.e.…”

“…Consequently, in most animals studied so far, the assessment of salt concentration drives acceptance or avoidance behavioral responses (1, 2). For example, low-salt (< 0.1 M) triggers insect feeding and oviposition, whereas high-salt (> 0.1 M) promotes avoidance and prevents egg-laying (3–9). Salts are detected by the taste system, a sensory modality that helps animals make predictions about the value of a potential food source, i.e.…”

“…For example, they avoid surfaces coated with high-NaCl or -KCl (1 M) (25, 26), preferring instead surfaces impregnated with salt concentrations similar to those of the human sweat (0.1 M) (24, 25). Furthermore, R. prolixus accepts or rejects a feeding solution depending on its NaCl or KCl concentration (3, 8). Many molecules produce insect avoidance due to the negative impact they may have on their physiology, i.e.…”