Characterization of crustacean cardioactive peptide‐like immunoreactivity in the horseshoe crab, Limulus polyphemus

Abstract

The localization of crustacean cardioactive peptide-like immunoreactivity in the horseshoe crab Limulus polyphemus was investigated with enzyme-linked immunosorbent assay and fluorescence microscopy. Immunoreactivity was quantified in the opisthosomal nervous system (67.7 +/- 11.4 ng/g), cardiac ganglion (45.0 +/- 10.3 ng/g), prosomal nervous system (28.5 +/- 6.6 ng/g), and midgut (24.6 +/- 6.7 ng/g). In the brain, immunoreactive somata were observed in ganglion cells of the central body, in the medullary group and within the ventral medial group. Clusters of immunoreactive cells were found in each of the circumesophageal, pedal ganglia, and in the opisthosomal, abdominal ganglia. In the periphery, immunoreactive varicose fibers were observed in branches of the intestinal nerves, and near longitudinal and circular muscle fibers of the midgut. Immunoreactivity was observed in the cardiac ganglion and myocardium of the neurogenic heart. Synthetic crustacean cardioactive peptide had slight excitatory effects on the cardiac rhythm at doses up to 10(-6) M. This peptide had excitatory effects on the midgut at nanomolar doses. Ventral nerve cord extracts were partially purified with reverse phase high performance liquid chromatography. Two regions of immunoreactivity were detected, one of which coeluted with the authentic peptide. The distribution of crustacean cardioactive peptide immunoreactivity is compared with other transmitter systems in the Limulus nervous system, and myotropic actions of this peptide are discussed with respect to peptidergic modulation of intestinal motility.

Modulation of Oscillator Interactions in the Crab Stomatogastric Ganglion by Crustacean Cardioactive Peptide

“…Although there is now an extensive literature documenting the presence of CCAP-like immunoreactivity in a large number of arthropod species (Cheung et al, 1992;Keller, 1992;Davis et al, 1993;Furuya et al, 1993;Lehman et al, 1993;Dircksen, 1994;Trube et al, 1994;Breidbach et al, 1995;Groome and Lehman, 1995;Würden and Homberg, 1995), the physiological actions of CCAP have been considerably less intensively studied. Although CCAP was initially named because of its cardioexcitatory actions on semi-isolated heart preparations of the crab C. maenas (Stangier et al, 1987), not all crustacean hearts seem to be sensitive to CCAP (McGaw et al, 1995).…”

“…Although CCAP was initially named because of its cardioexcitatory actions on semi-isolated heart preparations of the crab C. maenas (Stangier et al, 1987), not all crustacean hearts seem to be sensitive to CCAP (McGaw et al, 1995). Moreover, the few physiological studies that are now available show that CCAP is likely to act on numerous other target organs, such as the retina (Gaus and Stieve, 1992) and midgut (Groome and Lehman, 1995), and now the STG and associated stomach muscles. Preliminary experiments studying the effects of CCAP injections into intact and behaving crayfish (Nie␤en et al, 1995;Bo hm et al, 1996) show that CCAP accelerates the heartbeat, ventilation, and pyloric rhythm, and can initiate the gastric rhythm.…”

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

“…For a number of reasons we focused on CCAP as a potential modulator of anterior foregut motility around the time of MF ingestion. CCAP is a nonapeptide and acts as a neuroand myomodulator in a number of different arthropods (Breidbach et al, 1995;Groome and Lehman, 1995;McNeil et al, 1998;Mulloney et al, 1997). In the central nervous system (CNS) of M. sexta there are over 90 neurons that express the CCAP gene (Loi et al, 2001).…”

Limulus and heart rhythm

“…Moreover, in L. polyphemus , there is the “initial differentiation of sympathetic and vagus systems similar to those found in vertebrates” (Patten & Redenbaugh, ). Both the pro‐ and opisthosomal regions contain similar types of neurons, for example, those containing the crustacean cardioactive peptide (CCAP; Groome & Lehman, ). The CCAP immunoreactive fibers are the constituent of a bundle of the intestinal nerve.…”

“…Homologous CCAP has been isolated from the venom of Conus villepinii , the marine cone snail and, therefore termed as CCAP‐vil (Miloslavina et al, ). In L. polyphemus and mollusks, the CNS is encapsulated with a vascular sheath (Coggeshall, ; Groome & Lehman, ; V. Zhuravlev, Bugaj, Kodirov, Safonova, & Staruschenko, ) resembling the pia mater in vertebrates.…”