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Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001.

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Neuroscience. 2nd edition.

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Ligand-Gated Ion Channels

Many types of ion channels respond to chemical signals (ligands) rather than to changes in the membrane potential (Figure 4.4E-G). The most important of these ligand-gated ion channels in the nervous system is the class activated by binding neurotransmitters (Figure 4.4E). These channels are essential for synaptic transmission and other forms of cell-cell signaling phenomena discussed in Chapters 5–8. Whereas the voltage-gated ion channels underlying the action potential typically allow only one type of ion to permeate, channels activated by extracellular ligands are usually less selective, allowing two or more types of ions to pass through the channel pore.

Other ligand-gated channels are sensitive to chemical signals from within the cytoplasm of neurons (see Chapter 8). These channels have ligand-binding domains on their intracellular surfaces that interact with second messengers such as Ca2+ (Figure 4.4F) and the cyclic nucleotides cAMP and cGMP (Figure 4.4G). Such channels can be selective for specific ions such as K+ or Cl-, or can be permeable to all physiological cations. The main function of these channels is to convert intracellular chemical signals into electrical information. This process is particularly important in sensory transduction, where channels gated by cyclic nucleotides convert odors and light into electrical signals. Some intracellularly activated ion channels are in the cell surface membrane, but others are in intracellular membranes such as the endoplasmic reticulum. These latter channels are selectively permeable to Ca2+ and regulate the release of Ca2+ from the lumen of the endoplasmic reticulum into the cytoplasm. The Ca2+ released can then trigger a spectrum of cellular responses.

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By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.

Copyright © 2001, Sinauer Associates, Inc.
Bookshelf ID: NBK11150


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