Effects of Spiradoline Mesylate, a Selective κ-Opioid-Receptor Agonist, on the Central Dopamine System with Relation to Mouse Locomotor Activity and Analgesia

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Abstract
We characterized the angiotensin II (All) receptor in human aortic smooth muscle cells (HASMCs). This receptor binds [125I]Sar1, Ile8-angiotensin II with a high affinity of 0.20±0.04 nM and a low capacity of 5.3±0.4 fmol/mg protein (230±17 sites/cell). Based on the K1 values, the ranking order of [125I]Sar1, Ile8-AII binding inhibition was as follows: Sar1, Ile8AII > AII > Dup 753 > All > AI » PD 123319. The addition of AII to HASMCs induced a rapid, transient increase in intracellular free Ca2+ concentration followed by a lower, sustained phase. When extracellular Ca2+ was removed by adding 3 mM EGTA, this initial transient increase was not changed, but the sustained phase was abolished. These results revealed AII receptors in HASMCs to be of the type 1 receptor subtype, which induce Ca2+ mobilization mainly from intracellular Ca2+ stores.