Contractile effects of various vasoactive agents in small rat portal veins and hepatic arteries and the influence of sympathetic denervation on the noradrenaline response

Publisher Website
Google Scholar
Abstract
Contractile responses were studied in isolated tubal segments of branches of the rat portal vein (Ø≅300μm)and hepatic artery (Ø≅ 200μm).Portal veins were approximately three times more sensitive to noradrenaline (NA) than hepatic arteries. 5‐hydroxytryptamine contracted hepatic arteries concentration‐dependently, whereas it produced only weak and inconsistent contractions in portal veins. Vasopressin effectively contracted hepatic arteries, whereas it had no effect on portal veins. Both vessel types responded to prostaglandin F2αwith contractions, although the drug potency was relatively low (EC50> 10‐5mol I‐1)‐ Histamine and carbachol failed to induce (hepatic arteries) or caused only weak (portal veins) contractions. Microsurgical hepatic hilar denervation reduced the catecholamine content of the parenchyma to ≥ 25% of controls. In both portal veins and hepatic arteries, the denervation procedure increased the NA sensitivity by factors of 3.1 and 2.0, respectively. In non‐denervated livers, cocaine produced a similar increase of the NA sensitivity, whereas the drug had no significant effect in vessels from denervated animals. Thus, there was a marked difference between rat portal veins and hepatic arteries in their responsiveness to several contractile agents. Furthermore, the results of the present study indicate that the adrenergic nerves in both vessel types can be adequately removed by the microsurgical denervation procedure used.