Ion Channels

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Chapter: Essential pharmacology : Pharmacodynamics Mechanism Of Drug Action; Receptor Pharmacology

Proteins which act as ion selective channels participate in transmembrane signaling and regulate intracellular ionic composition. This makes them a common target of drug action


ION CHANNELS

 

Proteins which act as ion selective channels participate in transmembrane signaling and regulate intracellular ionic composition. This makes them a common target of drug action (Fig. 4.1B). Drugs can affect ion channels either through specific receptors (ligand gated ion channels, Gprotein operated ion channels or by directly binding to the channel and affecting ion movement through it, e.g. local anaesthetics which physically obstruct voltage sensitive Na+ channels. In addition, certain drugs modulate opening and closing of the channels, e.g.:

 

§  Quinidine blocks myocardial Na+ channels.

§  Dofetilide and amiodarone block myocardial delayed rectifier K+ channel.

§  Nifedipine blocks Ltype of voltage sensitive Ca2+ channel.

§  Nicorandil opens ATPsensitive K+ channels.

§  Sulfonylurea hypoglycaemics inhibit pancreatic ATPsensitive K+ channels.

§  Amiloride inhibits renal epithelial Na+ channels.

§  Phenytoin modulates (prolongs the inactivated state of) voltage sensitive neuronal Na+ channel.

§  Ethosuximide inhibits Ttype of Ca2+ channels in thalamic neurones



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