Innervation of the heart and aorta of Manduca sexta

SUMMARYCrustacean cardioactive peptide (CCAP) is a highly conserved arthropod neurohormone that is involved in ecdysis, hormone release and the modulation of muscle contractions. Here, we determined the CCAP gene structure in the malaria mosquito Anopheles gambiae, assessed the developmental expression of CCAP and its receptor and determined the role that CCAP plays in regulating mosquito cardiac function. RACE sequencing revealed that the A. gambiae CCAP gene encodes a neuropeptide that shares 100% amino acid identity with all sequenced CCAP peptides, with the exception of Daphnia pulex. Quantitative RT-PCR showed that expression of CCAP and the CCAP receptor displays a bimodal distribution, with peak mRNA levels in second instar larvae and pupae. Injection of CCAP revealed that augmenting hemocoelic CCAP levels in adult mosquitoes increases the anterograde and retrograde heart contraction rates by up to 28%, and increases intracardiac hemolymph flow velocities by up to 33%. Partial CCAP knockdown by RNAi had the opposite effect, decreasing the mosquito heart rate by 6%. Quantitative RT-PCR experiments showed that CCAP mRNA is enriched in the head region, and immunohistochemical experiments in newly eclosed mosquitoes detected CCAP in abdominal neurons and projections, some of which innervated the heart, but failed to detect CCAP in the abdomens of older mosquitoes. Instead, in older mosquitoes CCAP was detected in the pars lateralis, the subesophageal ganglion and the corpora cardiaca. In conclusion, CCAP has a potent effect on mosquito circulatory physiology, and thus heart physiology in this dipteran insect is under partial neuronal control. Supplementary material available online at

Section: Discussionsupporting

confidence: 81%

Cardioacceleratory function of the neurohormone CCAP in the mosquito Anopheles gambiae

Estévez‐Lao

Boyce

Honegger

et al. 2013

“…8F). At all the stages examined, the observed pattern and density of FM1-43 staining on the foregut was similar to that observed following synaptotagmin immunocytochemistry (Davis et al, 2001;Littleton et al, 1993; Fig. 8G,H).…”

Section: Fm1-43 Staining Reveals a Deficit In Presynaptic Activity Ofsupporting

confidence: 82%

Modulation of foregut synaptic activity controls resorption of molting fluid during larval molts of the mothManduca sexta

Bestman

Booker

2003

The regulation and organization of a variety of stereotyped behaviors are essential for many aspects of animal development. One such collection is a series of ecdysial-related motor programs that lead to the shedding of an insect's old cuticle during a molt. Like all insects, the growth of larval Manduca sexta moths is limited by its inelastic cuticle. Consequently, growing larvae undergo a series of molts in which the old cuticle is shed and replaced by a new, larger cuticle. The two ecdysial-related motor patterns that have been the focus of much attention are the pre-ecdysis and ecdysis motor programs, which serve to loosen and then propel the old cuticle off the insect at the end of the molt, respectively (Copenhaver and Truman, 1982;Miles and Weeks, 1991; Ž itňan and Adams, 2000). The analysis of these two simple motor programs has served as a model system for the role of hormones in coordinating stereotyped behaviors. However, pre-ecdysis and ecdysis behaviors define the end of a series of ecdysial-related motor patterns that can stretch over several days. The first external sign that a Manduca larva has entered the molt cycle is apolysis, or the detachment of the old and new cuticles from one another as molting fluid (MF), a cocktail of digestive enzymes, is secreted by the epidermis into the exuvial space (the space between the old and new cuticles) where it degrades and weakens the old cuticle. Once degraded, the digested components of the exuvia and the MF are absorbed, leaving behind a thin, papery outer cuticle to be shed during ecdysis.The secretion of MF and its resorption many hours later are among a series of molt-related events that must be precisely coordinated during the molt cycle. While the removal of the MF prior to ecdysis is a feature common to all insect molts, there is no consensus on the mechanisms used to remove the MF from the exuvial space. It has often been reported that MF is resorbed across the newly formed cuticle and epidermis (Jungreis, 1979;Reynolds and Samuels, 1996;Wigglesworth, 1972). This conclusion is based on the studies of the larval molt of the bug Rhodnius prolixus (Wigglesworth, 1933(Wigglesworth, , 1972 and the pupal-adult molt of the silkworm Hyalophora cecropia (Lensky et al., 1970;Passonneau and Williams, 1953). These studies concluded that MF is absorbed into the hemocoel by passing through pores in the new cuticle.There is also evidence suggesting that the gut serves as a route for the removal of MF. Wachter (1930) We examined the role of the foregut in the resorption of molting fluid (MF) from the exuvial space during the last larval-larval molt of the moth Manduca sexta. In intermolt larvae, the activity of the foregut is characterized by robust peristaltic contractions. With the onset of the molt, MF is secreted into the exuvial space where it digests and weakens the old cuticle. The appearance of MF in the exuvial space is accompanied by a dramatic reduction in the amplitude of the foregut contractions. Foregut peristalsis returned about halfway through ...

“…Klukas et al confirmed that these SEG neurons were CCAP-IR (Klukas et al, 1996), which was also consistent with neurons identified in the CCAP gene expression study (Loi et al, 2001). Lastly, Davis et al provided evidence for neurohemal release sites from the SEG of CCAP in the vicinity of the aorta and anterior foregut (Davis et al, 2001). Our finding of CCAP-IR neurohemal-like structures on the muscles of the anterior foregut (Fig.·4) is consistent with these previous studies.…”

Section: A Blood-borne Factor Acts To Suppress Anterior Foregut Motilitysupporting

confidence: 92%

“…Using CCAP antiserum, we labeled possible release sites on the muscles of the anterior foregut (shown in Fig.·4, the anterior foregut esophageal dilators). This labeling was reminiscent of CCAP-ir neurohemal structures found on other M. sexta tissues and in other species (Davis et al, 2001;Donini et al, 2002). With these data in mind, we wanted to test whether CCAP also plays a role in triggering the return of the peristaltic contractions of the anterior foregut observed at the end of the molt.…”

Section: P<0001)mentioning

confidence: 86%

“…We found it intriguing that one of the four pairs of CCAP-immunoreactive (CCAP-ir) neurons, which have been repeatedly identified in the subesophageal ganglion (SEG), has also been reported to send out processes terminating in the immediate region of the anterior foregut (Davis et al, 2001;Ewer et al, 1994;Klukas et al, 1996;Loi et al, 2001). Using CCAP antiserum, we labeled possible release sites on the muscles of the anterior foregut (shown in Fig.·4, the anterior foregut esophageal dilators).…”

Section: P<0001)mentioning

confidence: 93%

See 1 more Smart Citation

The control of anterior foregut motility during a larval molt of the moth Manduca sexta involves the modulation of presynaptic activity

Bestman

Booker

2006

motorneuron terminals and its actions are sufficient to trigger the dramatic increase in EJP amplitude and anterior foregut contractions. Finally, the surgical ablation of the subesophageal ganglion, which has been previously described to be a source of CCAP neurons and the CCAP projections to the anterior foregut region, blocks both the increase in anterior foregut motility and the ingestion of MF that normally occur at the end of a larval-larval molt.