Forscher P, Oxford G S, Schulz D
J Physiol. 1986 Oct;379:131-44. doi: 10.1113/jphysiol.1986.sp016244.
Averaged ensemble Ba currents were recorded from tissue cultured embryonic chick dorsal root ganglion (d.r.g.) cells using the cell-attached patch-clamp technique. Noradrenaline (NA) applied to extrapatch membrane had no clear consistent effect on drug-free patch currents. This finding supports a previous suggestion that second messengers may not be involved in NA-mediated decreases in Ca currents in sensory neurones (Forscher & Oxford, 1985). Cell-attached patch currents sometimes increased slowly after extrapatch application of NA, but were not reversibly decreased by drug treatment. Large patch currents were used to trigger cellular action potentials. NA reversibly decreased action potential duration as reflected in extracellularly recorded patch action currents. Simultaneously recorded inward patch currents were not affected. D.r.g. cell adenylate cyclase activity was assayed. NA did not affect intracellular cyclic AMP levels at concentrations which cause 30-70% decreases in gCa in dialysed cells (Forscher & Oxford, 1985). Treatment with forskolin (50 microM) or isoprenaline (10 microM) resulted in 60- and 2-fold increases respectively in adenylate cyclase activity over basal levels. These results suggest that NA decreases Ca currents by direct NA interactions with the Ca channel or a molecule tightly coupled to channel function in d.r.g. cells.
采用细胞贴附式膜片钳技术，从组织培养的鸡胚背根神经节（d.r.g.）细胞记录平均整合的Ba电流。施加于膜片外膜的去甲肾上腺素（NA）对无药物的膜片电流没有明显一致的影响。这一发现支持了之前的观点，即第二信使可能不参与NA介导的感觉神经元Ca电流降低（Forscher和Oxford，1985）。在膜片外施加NA后，细胞贴附式膜片电流有时会缓慢增加，但药物处理不会使其可逆性降低。大的膜片电流用于触发细胞动作电位。NA可逆性地缩短动作电位持续时间，这在细胞外记录的膜片动作电流中得到反映。同时记录的内向膜片电流不受影响。测定了d.r.g.细胞的腺苷酸环化酶活性。在能使透析细胞中gCa降低30 - 70%的浓度下，NA不影响细胞内环磷酸腺苷（cAMP）水平（Forscher和Oxford，1985）。用福斯高林（50 microM）或异丙肾上腺素（1 microM）处理分别使腺苷酸环化酶活性比基础水平提高60倍和2倍。这些结果表明，NA通过与d.r.g.细胞中的Ca通道或与通道功能紧密偶联的分子直接相互作用来降低Ca电流。
