Friedman D J, Duckles S P
Department of Pharmacology, College of Medicine, University of California, Irvine 92717.
Eur J Pharmacol. 1994 Jan 24;252(1):1-9. doi: 10.1016/0014-2999(94)90568-1.
Possible age-related changes in the roles of L- and N-type Ca2+ channels and dopamine D2 receptors in control of norepinephrine release were investigated in tail arteries of F-344 rats. Nifedipine had no effect on stimulation-evoked tritium efflux at 6 or 24 months of age; however, omega-conotoxin GVIA reduced efflux by 70 to 80% at both ages even when frequency of stimulation was altered. Activation of prejunctional dopamine D2 receptors by the selective agonist N-0923 [(S)-(-)-2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin++ +] inhibited contractile responses to transmural nerve stimulation in a frequency and concentration-dependent manner. Effects were similar from 6 to 26 months. Furthermore inhibition by N-0923 of stimulation-evoked [3H]norepinephrine efflux was not different at 12 and 24 months. Thus, N-type Ca2+ channels predominate in control of norepinephrine release, and this is unchanged with advancing age or stimulation intensity. Furthermore, D2 receptor-mediated inhibition of norepinephrine release is not altered with advancing age.
在F-344大鼠的尾动脉中，研究了L型和N型Ca2+通道以及多巴胺D2受体在去甲肾上腺素释放控制中可能的年龄相关变化。硝苯地平对6个月或24个月龄时刺激诱发的氚外流没有影响；然而，ω-芋螺毒素GVIA在两个年龄组均使外流减少70%至80%，即使刺激频率改变时也是如此。选择性激动剂N-0923 [（S）-（-）-2-（N-丙基-N-2-噻吩基乙氨基）-5-羟基四氢萘]对突触前多巴胺D2受体的激活以频率和浓度依赖的方式抑制对跨壁神经刺激的收缩反应。6至26个月龄时的效应相似。此外，N-0923对刺激诱发的[3H]去甲肾上腺素外流的抑制在12个月和24个月时没有差异。因此，N型Ca2+通道在去甲肾上腺素释放的控制中占主导地位，并且随着年龄增长或刺激强度增加这一点不变。此外，D2受体介导的去甲肾上腺素释放抑制不会随着年龄增长而改变。
