Callanan K M, Keenan A K
Br J Pharmacol. 1984 Nov;83(3):841-7. doi: 10.1111/j.1476-5381.1984.tb16240.x.
The stimulation-evoked release of tritium was measured from rat atria labelled with [3H]-noradrenaline. The calcium dependence of evoked release and the facilitation of this release via activation of presynaptic beta-adrenoceptors were examined using D600 (methoxyverapamil), nifedipine and dantrolene sodium. Both D600 and nifedipine at dose levels of 20 and 100 microM inhibited evoked release. Dantrolene (20, 100 microM) reduced release by 25%, the effect being maximal at 20 microM. In the presence of 20 nM isoprenaline, a facilitation of evoked release occurred, which was blocked by 0.1 microM (-)-propranolol. The facilitatory action of isoprenaline was abolished by omission of calcium from the buffer, or by D600 or nifedipine, (100 microM). In contrast, the response to isoprenaline was not modified by dantrolene (20, 100 microM). It is concluded that the evoked release of noradrenaline (NA) utilizes Ca from both intra- and extracellular sources and that isoprenaline increases NA secretion by promoting the depolarization-induced influx of Ca.
用[3H]-去甲肾上腺素标记大鼠心房，测定刺激诱发的氚释放。使用D600（甲氧基维拉帕米）、硝苯地平和丹曲林钠研究诱发释放的钙依赖性以及通过激活突触前β-肾上腺素能受体对这种释放的促进作用。剂量为20和100微摩尔的D600和硝苯地平均抑制诱发释放。丹曲林（20、100微摩尔）使释放减少25%，在20微摩尔时作用最大。在存在20纳摩尔异丙肾上腺素的情况下，诱发释放出现促进作用，该作用被0.1微摩尔（-）-普萘洛尔阻断。从缓冲液中去除钙，或使用D600或硝苯地平（100微摩尔）可消除异丙肾上腺素的促进作用。相反，丹曲林（20、100微摩尔）不改变对异丙肾上腺素的反应。结论是，诱发的去甲肾上腺素（NA）释放利用细胞内和细胞外来源的钙，异丙肾上腺素通过促进去极化诱导的钙内流增加NA分泌。
