Comparison of the haemodynamic actions of neuropeptide Y, angiotensin II and noradrenaline in anaesthetised cats.

Blood pressure, heart rate, cardiac output, renal flow and femoral flow were recorded in open-chested anaesthetised cats. Dose-response curves were constructed for neuropeptide Y, angiotensin II and noradrenaline after pretreatment with atropine sulphate. Neuropeptide Y, on a molar basis, was 7 and 120 times less potent than noradrenaline and angiotensin, respectively, in producing a 50 mm Hg rise in mean arterial blood pressure. The pressor effect of neuropeptide Y was characterised by dose-dependent increases in total peripheral, renal and femoral resistance with little change in cardiac output. Neuropeptide Y had a similar potency to noradrenaline in causing these resistance changes. However, the pressor response to noradrenaline was associated with a dose-dependent increase in cardiac output. The pressor action of neuropeptide Y was not attenuated by adrenoceptor blockade by phenoxybenzamine (5 mg kg-1) and propranolol (1 mg kg-1).