Ikeda S R, Schofield G G, Weight F F
Section of Electrophysiology, National Institute on Alcohol Abuse and Alcoholism, Rockville, MD 20852.
Neurosci Lett. 1987 Oct 16;81(1-2):123-8. doi: 10.1016/0304-3940(87)90351-x.
Somatostatin-like immunoreactivity has been reported to occur in the postganglionic neurons of sympathetic ganglia. We therefore investigated the effect of somatostatin (SOM) on the Ca2+ current in sympathetic neurons. Voltage-clamp recordings, using the whole-cell patch-clamp technique, were made from acutely isolated adult rat superior cervical ganglion (SCG) neurons in solutions (external and internal) designed to isolate Ca2+ currents. Application of 0.001-1.0 microM [D-Trp8]SOM resulted in a rapid, reversible and concentration-dependent decrease in the amplitude of the Ca2+ current evoked from a holding potential of -80 mV. The concentration-response relationship for SOM could be fitted to a single-site binding model with an apparent dissociation constant of 11 nM; the maximal attainable block of Ca2+ current by SOM was 50%. SOM also produced a pronounced slowing of the Ca2+ current rising phase, especially at more depolarized potentials. At higher concentrations (0.03-1.0 microM), prolonged application of SOM resulted in a progressive decrease in blocking ability. The results are consistent with a neurotransmitter and/or neuromodulator role for SOM in the sympathetic nervous system.
据报道，生长抑素样免疫反应性存在于交感神经节的节后神经元中。因此，我们研究了生长抑素（SOM）对交感神经元Ca2+电流的影响。采用全细胞膜片钳技术，在旨在分离Ca2+电流的溶液（外部和内部）中，对急性分离的成年大鼠颈上神经节（SCG）神经元进行电压钳记录。应用0.001 - 1.0微摩尔[D - Trp8]SOM导致从 - 80 mV的钳制电位诱发的Ca2+电流幅度迅速、可逆且浓度依赖性降低。SOM的浓度 - 反应关系可以用表观解离常数为11 nM的单位点结合模型拟合；SOM对Ca2+电流的最大可达到阻断率为50%。SOM还使Ca2+电流上升相明显减慢，尤其是在更去极化的电位下。在较高浓度（0.03 - 1.0微摩尔）时，长时间应用SOM导致阻断能力逐渐下降。这些结果与SOM在交感神经系统中作为神经递质和/或神经调节剂的作用一致。
