Spencer Nick J, Hennig Grant W, Smith Terence K
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA.
Am J Physiol Gastrointest Liver Physiol. 2002 May;282(5):G904-17. doi: 10.1152/ajpgi.00345.2001.
Using simultaneous intracellular recordings, we have characterized 1) electrical activity in the longitudinal muscle (LM) of isolated segments of guinea pig distal colon free to contract spontaneously and 2) extent of propagation of spontaneous action potentials around the circumference of the colon. In all animals, rhythmical spontaneous depolarizations (SDs) were recorded that are usually associated with the generation of action potentials. Recordings from pairs of LM cells, separated by 100 microm in the circumferential axis, revealed that each action potential was phase locked at the two electrodes (mean propagation velocity: 3 mm/s). However, at an increased electrode separation distance of 1 mm circumferentially, action potentials and SDs became increasingly uncoordinated at the two recording sites. No SDs or action potentials ever propagated from one circumferential edge to the other (i.e., 13 mm apart). When LM strips were separated from the myenteric plexus and circular muscle, rhythmically firing SDs and action potentials were still recorded. Atropine (1 microM) or tetrodotoxin (1 microM) either reduced the frequency of SDs or temporarily abolished activity, whereas nifedipine (1 microM) always abolished SDs and action potentials. Kit-positive interstitial cells of Cajal were present at the level of the myenteric plexus and circular and longitudinal muscle. In summary, SDs and action potentials in LM propagate over discrete localized zones, usually <1 mm around the circumference of the colon. Furthermore, in contrast to the classic slow wave, rhythmic depolarizations in LM appear to be generated by an intrinsic property of the smooth muscle itself and are critically dependent on opening of L-type Ca(2+) channels.
通过同步细胞内记录，我们已对以下内容进行了表征：1）豚鼠远端结肠离体节段中能够自发收缩的纵行肌（LM）的电活动，以及2）自发动作电位在结肠圆周周围的传播范围。在所有动物中，均记录到了通常与动作电位产生相关的节律性自发去极化（SDs）。对沿圆周轴相距100微米的成对LM细胞进行记录发现，每个动作电位在两个电极处呈锁相状态（平均传播速度：3毫米/秒）。然而，当圆周方向上电极间距增加到1毫米时，两个记录位点处的动作电位和SDs变得越来越不同步。从未有SDs或动作电位从一个圆周边缘传播到另一个圆周边缘（即相距13毫米）。当将LM条带与肌间神经丛和环形肌分离时，仍记录到有节律发放的SDs和动作电位。阿托品（1微摩尔）或河豚毒素（1微摩尔）要么降低SDs的频率，要么暂时消除活动，而硝苯地平（1微摩尔）总是消除SDs和动作电位。在肌间神经丛以及环形肌和纵行肌水平存在c-Kit阳性的Cajal间质细胞。总之，LM中的SDs和动作电位在离散的局部区域传播，通常在结肠圆周周围<1毫米。此外，与经典慢波不同，LM中的节律性去极化似乎是由平滑肌自身的内在特性产生的，并且严重依赖于L型Ca(2+)通道的开放。
