Nozaki M, Sperelakis N
Department of Physiology and Biophysics, College of Medicine, University of Cincinnati, Ohio 45267-0576.
Am J Physiol. 1989 Feb;256(2 Pt 2):H455-9. doi: 10.1152/ajpheart.1989.256.2.H455.
Pertussis toxin (PT) was used to investigate the possible involvement of an inhibitory GTP-binding protein (G protein) in neuromuscular transmission at the sympathetic nerve terminal of guinea pig mesenteric artery. When the intracellular microelectrode technique was used, the amount of transmitter released was evaluated by recording the amplitude of excitatory junction potentials (EJPs) in the vascular smooth muscle (VSM) cells. EJPs were evoked by perivascular nerve stimulation with brief square pulses. The amplitude of EJPs was depressed by exogenously applied norepinephrine (NE) (greater than or equal to 10(-7) M) or histamine (greater than or equal to 10(-7) M). However, these effects of NE and histamine on EJP amplitude were almost completely blocked in PT-pretreated VSM cells (2 x 10(-7) g/ml PT, 24 h at 21 degrees C). These effects of PT pretreatment were time and temperature dependent. In contrast, there was no significant change in the resting membrane potential (-70.1 +/- 2.1 mV) or input resistance (11.9 +/- 0.4 M omega) in the VSM cells after PT pretreatment. These results suggest that the effects of NE and histamine on EJP amplitude may be mediated by PT-sensitive G proteins in the presynaptic nerve terminal.
百日咳毒素（PT）被用于研究抑制性鸟苷三磷酸结合蛋白（G蛋白）是否可能参与豚鼠肠系膜动脉交感神经末梢的神经肌肉传递。当使用细胞内微电极技术时，通过记录血管平滑肌（VSM）细胞中兴奋性接头电位（EJP）的幅度来评估递质释放量。EJP由用短方波脉冲进行的血管周围神经刺激诱发。外源性应用去甲肾上腺素（NE）（大于或等于10⁻⁷M）或组胺（大于或等于10⁻⁷M）会使EJP的幅度降低。然而，在经PT预处理的VSM细胞（2×10⁻⁷g/ml PT，21℃下处理24小时）中，NE和组胺对EJP幅度的这些作用几乎完全被阻断。PT预处理的这些作用具有时间和温度依赖性。相比之下，PT预处理后VSM细胞的静息膜电位（-70.1±2.1mV）或输入电阻（11.9±0.4MΩ）没有显著变化。这些结果表明，NE和组胺对EJP幅度的作用可能由突触前神经末梢中对PT敏感的G蛋白介导。
