Effect of Dopamine on the Ca<sup>2+</sup>-dependent K<sup>+</sup> currents in Isolated Single Gastric Myocytes of the Guinea-pig
Effect of Dopamine on the Ca<sup>2+</sup>-dependent K<sup>+</sup> currents in Isolated Single Gastric Myocytes of the Guinea-pig
- Rhee, Poong-Lyul Lee, Sang-Jin Kim, Sung-Joon So, In-Suk Hwang, Sang-Ik Kim, Ki-Whan
- 대한생리학회
- 대한생리학회지
- 제27권 제2호
- 1993.12
- 139 - 150 (12 pages)
We have reported that dopamine potentiates spontaneous contractions dose-dependently in guinea-pig antral circular muscle strips (Hwang et al, 1991). To clarify the underlying excitatory mechanism of dopamine on the gastric smooth muscle, the effects of dopamine on voltage-dependent Ca<sup>2+</sup> currents and Ca<sup>2+</sup> -dependent K<sup>+</sup> currents were observed in enzymatically dispersed guinea-pig gastric myocytes using the whole-cell voltage-clamp technique. Experiments were also done using isometric tension recording and conventional intracellular microelectrode techniques. 1) The effect of dopamine on the spontaneous contraction of antral circular muscle strips of the guinea-pig was excitatory in a dose-dependent manner, and was blocked by phentolamine, an α-adrenoceptor blocker. 2) The slow waves were not changed by dopamine. 3) The voltage-operated inward Ca<sup>2+</sup> current was not influenced by dopamine. 4) The Ca<sup>2+</sup>-dependent K<sup>+</sup> outward current, which might reflect the changes of intracellular calcium concentration, was enhanced by dopamine. This effect was abolished by phentolamine. 5) The enhancing effect of dopamine on the Ca<sup>2+</sup> -dependent K<sup>+</sup> current disappeared with heparin which is known to block the action of InsP<sub>3</sub>. From these results, it is suggested that dopamine acts via InsP<sub>3</sub>-mediated Ca<sup>2+</sup> mobilization from intracellular stores and such action potentiates the spontaneous contraction of guinea-pig gastric smooth muscle.