L-glutamate conditionally modulates the K+ current of Müller glial cells.
L-Glutamate inhibits the K+ conductance that dominates the electrical behavior of a Müller glial cell. The effect of glutamate is enhanced by simultaneous exposure to dopamine. L-Glutamate acts at a metabotropic receptor that controls the K+ conductance through two pathways. A rapid pathway produces a partial inhibition in less than 2 s. Thereafter, a slow pathway progressively inhibits the conductance with a half-time of minutes. Pathways initiated by L-glutamate and dopamine appear to converge on and stimulate adenylyl cyclase. A subsequent step is the activation of a cAMP-dependent protein kinase, PKA. The local overflow of L-glutamate from active synapses may functionally remove K+ channels from nearby glial membranes. A uniform rise in extracellular L-glutamate concentration, as might occur during pathological conditions, should suppress a glial cell's K+ conductance and allow other voltage-dependent processes to be influenced by depolarization.
Schwartz
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EA
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
D037361:Adenylate Cyclase Toxin; D000557:Ambystoma; D000818:Animals; D002227:Carbazoles / Q000494:pharmacology; D004553:Electric Conductivity / Q000187:drug effects; D004558:Electric Stimulation; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D026121:Indole Alkaloids; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008959:Models, Neurological; D009457:Neuroglia / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012160:Retina / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D002227:Carbazoles; D005971:Glutamates; D026121:Indole Alkaloids; D015221:Potassium Channels; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D018698:Glutamic Acid; C023427:guanosine 5'-O-(2-thiodiphosphate); C049985:staurosporine aglycone; D011493:Protein Kinase C