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Home Forums Stump the Chump Doubt on CVS PathoPharmacology Reply To: Doubt on CVS PathoPharmacology

  • Philip Tisdall, MD

    June 30, 2020 at 3:26 pm

    <div>M3 works through a Gq receptor when there is no endothelial NO released due to dysfunction. This means that it acts through increased intracellular calcium, leading to vasoconstriction. Some blood vessels in the body are innervated by parasympathetic cholinergic fibers (e.g., coronary vessels). These nerves release ACh, which binds to muscarinic receptors on the smooth muscle and/or endothelium. It has been shown in many arterial vessels that M3 receptors located on the vascular endothelium are coupled to the formation of nitric oxide (NO), which causes vasodilation; however, ACh causes smooth muscle contraction through a smooth muscle M3 receptors (coupled to Gq-proteins and increased IP3) and M2 receptors (coupled to Gi-proteins and decreased cAMP) when formation of NO is blocked. This latter finding has been used to assess coronary vascular dysfunction in humans in which NO production is diminished in diseased coronary arteries. In contrast to other arteries, cerebral arteries appear to have M5 muscarinic receptors that produce vasodilation in response to ACh. (Source:</div>