1. Systemic hypotension, blunted cardiovascular responsiveness to noradrenaline and an abnormal hypertensive pressor response to a postural change have been described in cirrhotic patients.
2. We have examined the role of blunted responsiveness in these abnormalities by studying basal arterial blood pressure and its response to a postural change (vertical head-up 90° tilting) in conscious and pithed CCl4-treated (cirrhotic) rats, as well as assessing the pressor response to noradrenaline in vivo and the vascular contractile response to noradrenaline in vitro.
3. A diminished hypotensive response to a change in posture was found in pre-cirrhotic portal hypertensive rats, whereas an inverted hypertensive pressor response in the face of systemic hypotension occurred in the cirrhotic rats with portal hypertension.
4. The inverted pressor response was abolished in the pithed portal hypertensive cirrhotic rats.
5. The pressor response to noradrenaline in vivo in conscious cirrhotic rats and the vascular contractile responsiveness to noradrenaline in vitro were intact.
6. We conclude that blunted responsiveness to noradrenaline is not a contributory factor to the development of systemic hypotension or the inverted pressor response to a change in posture in cirrhosis.