title: The effects of small cardioactive peptide B on the isolated heart and gill of Aplysia californica.
abstract: Effects of small cardioactive peptide B on the physiology of the isolated heart and gill preparations from the mollusc Aplysia californica were examined. In addition, the effects of small cardioactive peptide B and FMRFamide (Phe-Met-Arg-Phe-NH2) on adenylate cyclase activity were compared in particulate fractions of heart and gill tissues, respectively. Small cardioactive peptide B was found to exert dose-dependent, reversible changes in cardiac activity when perfused through the isolated heart. The EC50 values effecting changes in heart rate and force of contraction were 3 X 10(-11) and 3 X 10(-10) M, respectively; minimum concentrations found to effect changes in heart rate and force of contraction were normally 10(-15) and 10(-12) M, respectively. However, some winter hearts demonstrated threshold sensitivity to small cardioactive peptide B at concentrations as low as 10(-17) M. When perfused through the isolated gill, small cardioactive peptide B was found to suppress the gill withdrawal response amplitude with a threshold concentration of 10(-14) M and an EC50 value of 3 X 10(-11) M. Suppression of the gill withdrawal response amplitude by small cardioactive peptide B was found to be dose dependent and reversible up to a concentration of 10(-9) M. At higher concentrations, the suppression tended to persist irreversibly. Small cardioactive peptide B stimulated adenylate cyclase activity in particulate fractions of both heart and gill tissues with an EC50 of 0.1 and 1.0 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001048:Aplysia / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D019835:FMRFamide; D005880:Gills / Q000187:drug effects / Q000502:physiology*; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D009479:Neuropeptides; D009842:Oligopeptides / Q000494:pharmacology*; D010477:Perfusion; D012701:Serotonin / Q000494:pharmacology; D012844:Sincalide / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D014668:Vasotocin / Q000494:pharmacology
chemical_list: D009479:Neuropeptides; D009842:Oligopeptides; D005576:Colforsin; D012701:Serotonin; D014660:Vasoactive Intestinal Peptide; D019835:FMRFamide; C041307:small cardioactive peptide B; D000262:Adenylyl Cyclases; D012844:Sincalide; D014668:Vasotocin