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MD Pharmacology NMC syllabus ~5 min read Recent advances last updated on 2026-06-30

Nitric Oxide

The L-arginine–NO–cGMP Signalling Axis — NOS Isoforms, Physiological Roles, NO Donors (Nitrates · Nitroprusside), Inhaled NO in PPHN/ARDS, sGC Stimulators & NOS Inhibitors

Introduction & discovery

  • Nitric oxide (NO) is an oxide of nitrogen that exists as a free radical with one unpaired electron; it is the smallest endogenous signal molecule and the only one that is a gas at body temperature.
  • Gasotransmitter — a labile, freely diffusible gaseous mediator synthesised on demand (not stored), acting over very short distances and not released by exocytosis; a key messenger in cardiovascular, nervous, inflammatory and other cells.
  • EDRF story — Furchgott & Zawadzki (1980) showed acetylcholine relaxes vascular smooth muscle only with intact endothelium — a denuded vessel does not relax — and proposed a soluble endothelium-derived relaxing factor (EDRF).
  • Identity & Nobel — Murad (1977) showed glyceryl trinitrate vasodilates by releasing NO; Ignarro (1987) identified EDRF as NO itself. Furchgott, Murad & Ignarro shared the 1998 Nobel Prize — EDRF is now understood to be NO.
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Nitric Oxide

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