Glutamate receptor desensitization and its role in synaptic transmission.
Responses of excitatory amino acid receptors to rapidly applied glutamate were measured in outside-out membrane patches from chick spinal neurons. The peak current varied with glutamate concentration, with a half-maximal response at 510 microM and a Hill coefficient near 2. Currents activated by 1 mM glutamate desensitized and recovered in two phases. The faster time constant was identical to the time constant of decay of synaptic currents, suggesting that glutamatergic synaptic currents are terminated, in part, by receptor desensitization. Steady-state desensitization was evident following application of only 2-3 microM glutamate, concentrations comparable to levels in the extracellular space in the intact brain. Thus, glutamate receptor desensitization can affect synaptic efficacy in two ways: at high concentrations, rapid desensitization of receptors may curtail synaptic currents; at low concentrations, there is a significant reduction in the number of activatable receptors.
Trussell
L O
LO
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 61130.
Fischbach
G D
GD
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000494:pharmacology / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D005971:Glutamates; D015221:Potassium Channels; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D018698:Glutamic Acid; D011188:Potassium