Corticotrophin releasing factor attenuates N-G-Nitro-L-arginine Methyl Ester induced increases in blood pressure in the anaesthetised rat

In vitro corticotrophin releasing factor (CRF) causes a prolonged endotheli um-dependent vasodilatation which is blocked by inhibitors of nitric oxide (NO) synthase (NOS). Here the role of NO in CRF-induced reductions in blood pressure (BP) has been investigated using anaesthetised rats. Infusion of N-G-Nitro-L-arginine Methyl Ester (L-NAME) increased mean arterial pressure (MAP) but did not reduce the fall in BP caused by CRF injection. Bolus inj ection of L-NAME produced a marked vasopressor effect when given alone. How ever, when administered 20 min after CRF, L-NAME restored MAP to basal leve ls, but the marked vasopressor response observed in control animals was com pletely blocked. This indicates that the increase in BP occurring on bolus injection of L-NAME is not simply due to an inhibition of NO-dependent vaso dilatation.