Contractions of the whole and longitudinally cut rat's portal vein.

To investigate the role of lateral interactions, we quantified spontaneous contractions of whole and longitudinally cut rat's portal vein in vitro. The disruption of the wall had no effect on basic frequency determined from spectra and complexity index (CI) calculated by multiscale entropy analysis. Endothe-lium was disrupted and nonfunctional in all samples. Considering amplitude, frequency and CI we identified two modes of contractions. Neither mode of contractions nor the effect of aminopyridine (4-AP) depended on the integrity of the wall. We concluded that contractions in vitro originate in smooth muscle cells without involvement of the endothelium and lateral interactions. [ABSTRACT FROM AUTHOR]