The mechanism of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor desensitization after removal of glutamate.
We have examined responses of AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate) receptors in the chick nucleus magnocellularis to pairs of pulses of glutamate and determined the extent of desensitization and the rate of recovery. Receptors recovered from desensitization with a time constant of 16 ms, regardless of the concentration or duration of the conditioning pulse. Even with very brief conditioning pulses, evoking submaximal currents, desensitization occurred at a consistent rate after the removal of free ligand. A quantitative kinetic model based on these data shows that receptors must desensitize from a closed state. The results provide evidence that very brief exposure to glutamate, on the time scale of uniquantal synaptic transmission, will result in a significant reduction in sensitivity of postsynaptic receptors.
Raman
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Neuroscience Training Program, University of Wisconsin Medical School, Madison 53706.
Trussell
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D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002642:Chick Embryo; D017626:Cochlear Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018698:Glutamic Acid / Q000494:pharmacology*; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D007700:Kinetics; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018091:Receptors, AMPA / Q000187:drug effects* / Q000378:metabolism
D018091:Receptors, AMPA; D018698:Glutamic Acid; D007608:Kainic Acid