Pharmacodynamics of the adrenaline induced rise in portal pressure in dogs

ABSTRACT

"Ten mongrel dogs were used to study the effect of mepyramine maleate [H[1]-blocker] and/or phentolamine hydrochloride on the adrenaline-induced changes in portal pressure and systemic arterial pressure. Through the cannulated portal vein, adrenaline injection [2 micro g/Kg] induced a significant rise in portal pressure and systemic arterial pressure. When mepyramine maleate [1 mg/Kg] was injected prior to adrenaline, the increased portal pressure diminished whereas the increased systemic arterial pressure was potentiated. When phentolamine hydrochloride [1 mg/Kg] was injected prior to adrenaline, the rise in portal pressure was lower than the rise obtained in the previous two experiments, whereas the systemic arterial pressure dropped to near normal values. When the animals were pretreated by mepyramine and phentolamine, adrenaline failed to produce a rise in both portal pressure and systemic arterial pressure. These findings demonstrate that the rise in portal pressure in dogs following adrenaline injection via the portal vein is mainly through activation of alpha-receptors in the portal radicles and suggest, in addition, that its effect is possibly through indirect histamine release from the portal tree