Force, membrane potential and cytoplasmic Ca2+ responses to cyclic nucleotides in rat anococcygeus muscle

Gregory L. Raymond, Mary A. Tonta, Helena C. Parkington, Igor R. Wendt

Research output: Contribution to journalArticlepeer-review

Abstract

Simultaneous recordings of membrane potential and force, and cytoplasmic calcium ([Ca2+](i)) and force were made in rat anococcygeus to determine whether membrane hyperpolarisation plays a role in cyclic nucleotide-induced relaxation. In the presence of phenylephrine (0.2 μM), which evoked sustained contraction, an elevation in [Ca2+](i), and depolarisation, nitroprusside (5 μM) caused 96±3% relaxation, 77±3% decrease in suprabasal [Ca2+](i), and 16±2 mV hyperpolarisation. Forskolin (1 μM) caused 98±1% relaxation, 92±2% decrease in suprabasal [Ca2+](i), and 18±1 mV hyperpolarisation. These responses persisted in the presence of a variety of K+ channel blockers or in ouabain. The decrease in [Ca2+](i) preceded the commencement of relaxation whereas the onset of hyperpolarisation lagged behind. Thus, cyclic nucleotide-mediated relaxation in rat anococcygeus is not dependent on hyperpolarisation mediated by the opening of K+ channels. Rather, it is suggested that the decrease in [Ca2+](i) gives rise to hyperpolarisation, which reflects a decline in the Ca2+ dependent conductance(s) activated by phenylephrine. Copyright (C) 1998 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)183-192
Number of pages10
JournalEuropean Journal of Pharmacology
Volume362
Issue number2-3
DOIs
Publication statusPublished - 4 Dec 1998
Externally publishedYes

Keywords

  • Anococcygeus
  • Ca, intracellular
  • K channel blocker
  • Membrane potential
  • Ouabain
  • Smooth muscle

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