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A comparison of the inhibitory effects of sodium nitroprusside, pinacidil and nifedipine on pressor response to N G ‐nitro‐ l ‐arginine
Author(s) -
Wang YongXiang,
Zhou Ting,
Pang Catherine C.Y.
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb12816.x
Subject(s) - sodium nitroprusside , nifedipine , pinacidil , inhibitory postsynaptic potential , chemistry , pharmacology , arginine , vasodilation , medicine , endocrinology , nitric oxide , biochemistry , calcium , glibenclamide , diabetes mellitus , amino acid
1 The inhibitory effects of sodium nitroprusside (SNP), a nitric oxide (NO) donor, on mean arterial pressure (MAP) responses to N G ‐nitro‐ l ‐arginine ( l ‐NNA) (NO synthase inhibitor), angiotensin II (AII) and noradrenaline (NA) were compared with those of pinacidil (K ATP channel opener) and nifedipine (L‐type calcium antagonist) in conscious, unrestrained rats. 2 Intravenous bolus injections of l ‐NNA (1–64 mg kg −1 ), AII (0.02–1.28 μg kg −1 ) and NA (0.25–16 μg kg −1 ) dose‐dependently increased MAP to similar maxima. Intravenous infusions of SNP (1, 4 and 16 μg kg −1 min −1 ) dose‐dependently increased ED 50 s of l ‐NNA, AII and NA. However, the maximum response evoked by l ‐NNA, but not by AII nor NA, was dose‐dependently reduced by SNP. Moreover, the inhibitory effect of SNP on the pressor response to l ‐NNA ceased when the infusion of SNP was terminated. 3 Pinacidil (80 μg kg −1 min −1 for 30 min followed by 5 μg kg −1 min −1 ) increased ED 50 s of l ‐NNA, AII and NA but did not decrease the maximum responses to any of these agents. 4 Nifedipine (1 mg kg −1 min −1 ) non‐selectively reduced maximum responses to l ‐NNA, AII and NA to similar levels and increased ED 50 s of AII and NA but not l ‐NNA. 5 The results show that SNP causes a selective, non‐competitive and reversible inhibition of the pressor response to l ‐NNA. This inhibition by SNP is unlikely to be related to hypotension, the opening of ATP‐sensitive potassium channels or blockade of L‐type calcium channels.