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Serotonin에 의한 가토 신동맥 평활근 수축기전

Contractile Mechanisms of Serotonin in the Renal Arterial smooth muscle of a Rabbit

The contractile mechanisms of serotonin were investigated in the renal artery of a rabbit. The helical strips of isolated renal artery were immersed in the normal or Ca<sup>2+</sup>-free tris-buffered Tyrode s solution, which was equilibrated with 100% O<sub>2</sub> at 35℃. The contraction by serotonin or norepinephrine (NE) began at 1 X 10<sup>-7</sup> M and reached the maximal contraction at 1 X 10<sup>-5</sup> M. The maximal contraction by serotonin corresponded to 58.1±4.2% of maximal contraction by NE. Cyproheptadine, a serotonin receptor blocker, shifted the concentration-response curve to the right without any reduction in the maximum response but shifted that of NE to the right with reduction in maximum response. And phentolamine, an α-receptor blocker, shifted the concentration-response curve of serotonin or NE without any reduction in maximum responses. The pA<sub>2</sub> values for cyproheptadine against serotonin and NE were 10.35±0.04 and 8.45±0.13, respectively. The pA<sub>2</sub> values for phentolamine against serotonin and NE were 6.87±0.04 and 8.14±0.08, respectively. after the pretreatment with 6-hydroxydopamine, the contraction induced by 100 mM K<sup>+</sup>, tyramine and serotonin reduced to 83.0±2.0, 26.8±6.2 and 82.0±3.5% of control, respectively. The contraction by serotonin in the Ca<sup>2+</sup>-free Tyrode s solution was increased and sustained with the addition of Ca<sup>2+</sup> extracellulary. The serotonin-sensitive intracellular Ca<sup>2+</sup> pool was depleted completely by the pretreatment with NE, but the NE-sensitive intracellular Ca<sup>2+</sup> pool was depleted partially by the pretreatment with serotonin. From the above results, it is suggested that the contraction induced by serotonin in the renal artery of a rabbit may be due to mechanisms in which serotonin acts directly on specific serotonin receptors and also acts indirectly on α-adrenoceptors by displacing NE from neuronal stores.

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