Activation of a divalent cation-conducting channel in heart ventricle muscle cells of the snail Lymnaea stagnalis by the molluscan cardioactive peptide FMRFamide.
Ion channels with characteristics of Ca2+ channels have been found in isolated heart ventricle cells of the snail Lymnaea stagnalis. Although spontaneous Ca2+ or Ba2+ currents were seen only occasionally, spontaneous inward Na+ currents were readily observed in the absence of patch pipette Ca2+ between membrane potentials of -100 mV and +20 mV. These currents were blocked by 2 mM Ni2+, 2 mM Co2+ and 10 microM Ca2+. The channels usually ceased conducting within a few minutes after seal formation with the patch pipette and could not be re-activated with depolarizing voltage steps. However, at the cell's resting potential, 10(-8) to 10(-6) M of the molluscan cardioactive peptide FMRFamide or its analogue FLRFamide2+ applied to the cell membrane away from the patch pipette, induced unitary Ba2+ currents or, in the absence of Ca2+ in the patch pipette, Na+ currents. This suggests that a secondary messenger is involved in the FMRFamide-induced activation of these channels rather than a direct activation of a channel-receptor complex by the peptide.
Brezden
B L
BL
Ottawa-Carleton Institute of Biology, Carleton University, Ontario, Canada.
Benjamin
R P
RP
Gardner
D R
DR
D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002413:Cations, Divalent / Q000378:metabolism; D019835:FMRFamide; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D007447:Invertebrate Hormones / Q000737:chemistry / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D008195:Lymnaea / Q000378:metabolism*; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D009479:Neuropeptides / Q000737:chemistry / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism
D015220:Calcium Channels; D002413:Cations, Divalent; D007447:Invertebrate Hormones; D007473:Ion Channels; D009479:Neuropeptides; D001464:Barium; D019835:FMRFamide; D012964:Sodium