Force, membrane potential and cytoplasmic Ca2+ responses to cyclic nucleotides in rat anococcygeus muscle
| Autor: | Helena C. Parkington, Gregory L. Raymond, Igor R Wendt, Mary A Tonta |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Male
Nitroprusside Cytoplasm medicine.medical_specialty Potassium Channels Vasodilator Agents chemistry.chemical_element Calcium Ouabain Membrane Potentials Rats Sprague-Dawley Phenylephrine Cyclic nucleotide chemistry.chemical_compound Internal medicine Potassium Channel Blockers medicine Animals Vasoconstrictor Agents Drug Interactions Channel blocker Pharmacology Membrane potential Forskolin Colforsin Muscle Smooth Depolarization Rats Endocrinology chemistry Nucleotides Cyclic Muscle Contraction medicine.drug |
| Zdroj: | European Journal of Pharmacology. 362:183-192 |
| ISSN: | 0014-2999 |
| Popis: | 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 microM), which evoked sustained contraction, an elevation in [Ca2+]i, and depolarisation, nitroprusside (5 microM) caused 96+/-3% relaxation, 77+/-3% decrease in suprabasal [Ca2+]i, and 16+/-2 mV hyperpolarisation. Forskolin (1 microM) 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. |
| Databáze: | OpenAIRE |
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