Regulation by second messengers of the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes

A. E. Busch, M. P. Kavanaugh, M. D. Varnum, John Adelman, R. A. North

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Abstract

1. Voltage-clamp recordings of membrane current were made from Xenopus oocytes that had been injected with RNA which had been transcribed in vitro from a cloned complementary DNA. 2. Depolarization from -80 mV evoked outward potassium currents that developed very slowly. At -20 mV the time constant for activation was about 50 s and at +40 mV about 6 s. 3. The potassium current was increased by the calcium ionophore A23187 or by intracellular injection of inositol 1,4,5-trisphosphate (IP3), each of which should increase the intracellular calcium concentration ([Ca2+](i)). The current was decreased by injection of BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid). The current was also reduced by phorbol esters; this effect was blocked by staurosporine. 4. In oocytes that had also been injected with RNA encoding the 5-hydroxytryptamine (5-HT2) receptor, 5-HT increased the potassium current. After caffeine pretreatment, to block the release of intracellular calcium, 5-HT decreased the current; this decrease was prevented by staurosporine. 5. It is concluded that the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes is increased by increases in [Ca2+](i) and is decreased by activation of protein kinase C. Stimulation of 5-HT2 receptors can have both these effects, but the former normally predominates.

Original languageEnglish (US)
Pages (from-to)491-502
Number of pages12
JournalJournal of Physiology
Volume450
Publication statusPublished - 1992

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ASJC Scopus subject areas

  • Physiology

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Busch, A. E., Kavanaugh, M. P., Varnum, M. D., Adelman, J., & North, R. A. (1992). Regulation by second messengers of the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes. Journal of Physiology, 450, 491-502.