Modulation of appetite and feeding behavior of the larval mosquito Aedes aegypti (L.) by the serotonin-selective reuptake inhibitor paroxetine: shifts between distinct feeding modes and the influence of feeding status.

Abstract

The effects of the serotonin-selective reuptake inhibitor paroxetine (2×10 -5 mol l -1) on behavior of the larval mosquito Aedes aegypti are described. Four discrete behavioral states dominate larval behavior: wriggling, two distinct types of feeding, and quiescence. Feeding behaviors consist of foraging along the bottom of the container (substrate browsing), and stationary filter feeding while suspended from the surface film. Fed larvae respond to paroxetine with increased wriggling, and reductions in both feeding behaviors. In contrast, food-deprived larvae treated with paroxetine show no change in the proportion of time spent wriggling or feeding, but shift from stationary filter feeding to substrate browsing. Thus, actions of paroxetine in fed larvae are consistent with suppression of appetite and stimulation of wriggling, whereas paroxetine causes fooddeprived larvae to switch from one feeding behavior to another. Further analysis of unfed larvae revealed that paroxetine decreased the power stroke frequency during wriggling locomotion, but had no effect on the swimming velocity during either wriggling or substrate browsing. These data suggest that: (1) serotonergic pathways may trigger shifts between distinct behaviors by actions on higher level (brain) integrating centers where behaviors such as feeding and locomotion are coordinated; (2) these centers in fed and fooddeprived larvae respond differently to serotonergic stimulation suggesting sensory feedback from feeding status; and (3) serotonergic pathways also modulate central pattern generators of the nerve cord where the bursts of action potentials originate that drive the rhythmic muscle contractions of wriggling.

Serotonin in Animal Cognition and Behavior

“…This includes flatworms [58], cnidarians [59], nematodes [60], annelids [61,62], arthropods (insects and crustaceans, [63][64][65]), and mollusks [66][67][68][69]. Part of our knowledge comes from studies investigating the ecological/toxicological consequences of SSRIs used as antidepressants, released in sanitary water, and finally spread in rivers [63,65,[70][71][72]. It also comes from studies stimulated by the need to develop new ecological intervention to decrease or eradicate associated pathologies to promote human health [58,73].…”

The pharmacological and functional characterization of the serotonergic system in Anopheles gambiae and Aedes aegypti: influences on flight and blood-feeding behavior

“…Serotonergic neurotransmission also potentially modulates blood-feeding behavior. Evidence in multiple insect species including the honeybee, ant, locust, cockroach, and fly, demonstrates that 5-HT innervation causes a reduction in feeding 27,28 . Our fluoxetine and PCPA ethyl ester data favor this argument, though further work is required to validate it.…”

The neurotransmitters serotonin and glutamate accelerate the heart rate of the mosquito Anopheles gambiae

“…In insects, serotonin is also present in the hemolymph, where it acts peripherally as a neurohormone (Chapman et al, 2013;Harrison et al, 2012;Klowden, 2013;Lange et al, 1989). Serotonin modulates feeding behavior, salivation, diuresis, muscle activity, and other processes in a wide variety of insect taxa (Clark et al, 1999;Falibene et al, 2012;Kinney et al, 2014;Maddrell et al, 1991;Novak et al, 1995;Orchard, 2006). Serotonin also influences the frequency of heart contractions in multiple insect species.…”

“…In mosquitoes, serotonin (also known as 5-hydroxytryptamine or 5-HT) is involved in feeding behavior, salivation, the transport of ions across the midgut and the Malpighian tubules, and the regulation of hemolymph composition (Clark and Bradley, 1997;Clark et al, 1999;Clark et al, 2009;Kinney et al, 2014;Novak et al, 1995;Novak and Rowley, 1994). Less is known about the function of glutamate in mosquitoes, but a significant body of work performed in other insects has shown that glutamate is released by motor neurons at the neuromuscular junction, which initiates the depolarization of the sarcolemma and leads to the contraction of muscle (Harrison et al, 2012).…”