Hepatic veins belong to "the veins of the digestive tube" in the dog.

Pharmacological responsiveness of isolated strips of the canine hepatic veins was investigated. Circular strips showed a low responsiveness to 5-hydroxytryptamine, a low sensitivity to norepinephrine and a high sensitivity to histamine. Longitudinal strips developed greater tensions to norepinephrine than circular strips. An excitatory cholinergic component was demonstrated in contractile responses of longitudinal strips to transmural stimulation. Acetylcholine-induced contraction was potentiated by physostigmine. These results indicate that the hepatic veins belong to the group of "veins of the digestive tube".