title: Evidence dromyosuppressin acts at posterior and anterior pacemakers to decrease the fast and the slow cardiac activity in the blowfly Protophormia terraenovae.
abstract: The molecular complexity of the simple blowfly heart makes it an attractive preparation to delineate cardiovascular mechanisms. Blowfly cardiac activity consists of a fast, high-frequency signal phase alternating with a slow, low-frequency signal phase triggered by pacemakers located in the posterior abdominal heart and anterior thoracocephalic aorta, respectively. Mechanisms underlying FMRFamide-related peptides (FaRPs) effects on heart contractions are not well understood. Here, we report antisera generated to a FaRP, dromyosuppressin (DMS, TDVDHVFLRFamide), recognized neuronal processes that innervated the blowfly Protophormia terraenovae heart and aorta. Dromyosuppressin caused a reversible cardiac arrest. High- and low-frequency signals were abolished after which they resumed; however, the concentration-dependent resumption of the fast phase differed from the slow phase. Dromyosuppressin decreased the frequency of cardiac activity in a dose-dependent manner with threshold values between 5 fM and 0.5 fM (fast phase), and 0.5 fM and 0.1 fM (slow phase). Dromyosuppressin structure-activity relationship (SAR) for the decrease of the fast-phase frequency was not the same as the SAR for the decrease of the slow-phase frequency. The alanyl-substituted analog TDVDHVFLAFamide ([Ala9] DMS) was inactive on the fast phase, but active on the slow phase, a novel finding. FaRPs including myosuppressins are reported to require the C-terminal RFamide for activity. Our data are consistent with the conclusions DMS acts on posterior and anterior cardiac tissue to play a role in regulating the fast and slow phases of cardiac activity, respectively, and ligand-receptor binding requirements of the abdominal and thoracocephalic pacemakers are different.
authors.affiliation: Dipartimento di Biologia Sperimentale, Sezione di Fisiologia Generale, Università di Cagliari, 09042 Monserrato-Cagliari, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Angioy
authors.forename: Patrizia
authors.initials: P
authors.lastname: Muroni
authors.forename: Iole Tomassini
authors.initials: IT
authors.lastname: Barbarossa
authors.forename: Jennifer
authors.initials: J
authors.lastname: McCormick
authors.forename: Ruthann
authors.initials: R
authors.lastname: Nichols
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D004175:Diptera / Q000187:drug effects* / Q000502:physiology*; D004562:Electrocardiography; D006321:Heart / Q000187:drug effects / Q000502:physiology; D007150:Immunohistochemistry; D007301:Insect Hormones / Q000737:chemistry / Q000494:pharmacology* / Q000502:physiology*; D008297:Male; D009479:Neuropeptides / Q000737:chemistry / Q000494:pharmacology* / Q000502:physiology*; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology
chemical_list: D007301:Insect Hormones; D009479:Neuropeptides; D010446:Peptide Fragments; C077905:neomyosuppressin