Cs+ was used to study the mechanisms involved in the induction of haemodynamic and metabolic oscillations in the isolated rat liver perfused by the portal vein. 2. Cs+ (2.25 mM) in K(+)-free perfusate causes the appearance of periodic increases in portal pressure (3.87 +/- 0.6 mmHg, n = 24) and decreases in O2 uptake (111 +/- 26 microM) at a frequency of 0.013 +/- 0.002 Hz. A 19.8 +/- 1.2 min induction time occurs prior to the generation of periodicity. The oscillations are interspersed with low amplitude shoulders and peaks indicating multiple non-phasic components. 3. Cs+ concentrations higher or lower than 2.25 mM decrease oscillation amplitude and render them aperiodic. No oscillations are observed with 0.5 or 12.5 mM Cs+. 4. The oscillations are reversibly blocked by 1 mM K+, 1 mM EGTA, 5 microM verapamil or 0.17 microM tetrodotoxin. One micromolar chlorpheniramine, 10 microM propranolol, 12 microM phentolamine or 35 microM atropine also maximally inhibit the Cs(+)-induced vasoactivity. 5. The results show that the liver perfused by the portal vein has all of the components required to activate vascular synchrony including intrinsic neural input and responsive vasoactive cells.
