Malpighian tubules of larvalAedes aegypti are hormonally stimulated by 5-hydroxytryptamine in response to increased salinity

Summary A role for the rectum in the ionoregulatory homeostasis of larval Chironomus riparius was revealed by rearing animals in different saline environments and examining: (1) the spatial distribution and activity of keystone ionomotive enzymes Na+-K+-ATPase (NKA) and V-type H+-ATPase (VA) in the alimentary canal and (2) rectal K+ transport with scanning ion-selective electrode technique (SIET). NKA and VA activity were measured in four distinct regions of the alimentary canal as follows: the combined foregut and anterior midgut (FAMG), the posterior midgut (PMG), the Malpighian tubules (MT) and the hindgut (HG). Both enzymes exhibited 10 - 20 times greater activity in the HG relative to all other areas. When larvae were reared in either ion-poor water (IPW) or freshwater (FW), no significant difference in HG enzyme activity was observed. However, in brackish water (BW) reared animals, NKA and VA activity in the HG significantly decreased. Immunolocalization of NKA and VA in the HG revealed that the bulk of protein was located in the rectum. Therefore K+ transport across the rectum was examined using SIET. Measurement of K+ flux along the rectum revealed a net K+ reabsorption which was reduced four-fold in BW-reared larvae versus larvae reared in FW or IPW. Inhibition of NKA with ouabain, VA with bafilomycin and K+ channels with charybdotoxin, diminished rectal K+ reabsorption in FW- and IPW-reared larvae, but not BW-reared larvae. Data suggest that the rectum of C. riparius plays an important role in allowing these larvae to cope with dilute as well as salinated environmental conditions.

Section: Introductionmentioning

confidence: 71%

Tissue specific ionomotive enzyme activity and K+ reabsorption reveal the rectum as an important ionoregulatory organ in larvalChironomous ripariusexposed to varying salinity

Jonusaite

Kelly

Donini

2013

“…Serotonin stimulates acid/base transport of the larval mosquito midgut, and fluid secretion by the Malpighian tubules (Clark and Bradley, 1996;Clark and Bradley, 1997;Clark et al, 1999;Onken et al, 2008;Onken and Moffett, 2009); actions likely to be associated with feeding. However, Clark and Bradley detected no changes in hemolymph serotonin levels of larval A. aegypti in response to feeding status (Clark and Bradley, 1997). It is possible that a different feeding or assay protocol than used by Clark and Bradley would trigger detectable serotonin release, or that serotonin regulates midgut transport by synaptic or local control rather than by neuroendocrine mechanisms and thus does not increase in the hemolymph in response to feeding activity.…”

Section: Effects Of Paroxetine On Wriggling Locomotionmentioning

confidence: 81%

“…Serotonin is also involved in regulation of peripheral tissues in larval A. aegypti, but the role of serotonin in the physiological responses of larval A. aegypti to feeding are less clear than in Rhodnius. Serotonin stimulates acid/base transport of the larval mosquito midgut, and fluid secretion by the Malpighian tubules (Clark and Bradley, 1996;Clark and Bradley, 1997;Clark et al, 1999;Onken et al, 2008;Onken and Moffett, 2009); actions likely to be associated with feeding. However, Clark and Bradley detected no changes in hemolymph serotonin levels of larval A. aegypti in response to feeding status (Clark and Bradley, 1997).…”

Section: Effects Of Paroxetine On Wriggling Locomotionmentioning

confidence: 99%

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.

Kinney

Panting

Clark

2013

Self Cite

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.

“…Serotonergic pathways are known to regulate ion and fluid transport properties, acid-base transport and/or muscular motility of multiple organs, including salivary glands, midgut, oviduct and Malpighian tubules (e.g. Farmer et al, 1981;Barrett et al, 1993;Clark and Bradley, 1997;Clark et al, 1999;Lange et al, 1989;Maddrell et al, 1991;Maddrell et al, 1993;Onken et al, 2004;Onken et al, 2008;Orchard et al, 1988). In the larval mosquito Aedes aegypti, serotonin stimulates fluid and ion transport by the Malpighian tubules and ion and acid-base transport across the midgut (Clark and Bradley, 1996;Clark and Bradley, 1997;Clark et al, 1999;Onken et al, 2004;Onken et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Alaproclate and 6-nitroquipazine (DU 24565) are serotonin reuptake inhibitors in vertebrates (Classen et al, 1984;Rawlow et al, 1983). Of these agents, only methiothepin has previously been used in studies of insect systems (Troppmann et al, 2007;Clark and Bradley, 1997). In the larval mosquito A. aegypti, methiothepin blocks stimulation of Malpighian tubule fluid and ion secretion by serotonin (Clark and Bradley, 1997).…”

Section: Introductionmentioning

confidence: 99%

Effects of serotonergic agents on survival and hemolymph composition of the larval mosquitoAedes aegypti(Diptera: Culicidae, L.)in vivo: does serotonin regulate hemolymph acid–base homeostasis?

Clark

Lawecki

Shepherd

et al. 2009

SUMMARYThe role of serotonin in the regulation of larval Aedes aegypti hemolymph composition was investigated in vivo using two reuptake inhibitors (SSRIs), alaproclate HCl and 6-nitroquipazine maleate, and the receptor antagonist methiothepin mesylate. Larvae were placed in media differing in pH and salinity in the presence and absence of serotonergic agents. The toxicity of each agent was strongly influenced by ambient pH. For each agent, toxicity was negligible in acidic media, intermediate in neutral media and greatest in alkaline media. By contrast, toxicity of all agents was independent of salinity. No effects on mass-specific body water or hemolymph volume were observed whereas hemolymph osmotic pressure, Na + concentrations and pH differed significantly among treatments. 6-nitroquipazine caused a decrease in Na + from 115±1.7 to 103±0.9mmoll , respectively) whereas these agents did not influence acid excretion rates in pH 7 or pH 11 media. The hypothesis that serotonin is involved in hemolymph acid-base balance is discussed.