Time-dependent reduction of glutamate current in retinal bipolar cells.
Glutamate hyperpolarizes retinal depolarizing bipolar cells (DBCs) by decreasing a non-specific cation conductance. We have investigated this action of glutamate using whole-cell voltage clamp of DBCs in larval tiger salamander retinal slices and here report two observations: a wash-out of the glutamate response and a concomitant decrease in resting membrane conductance. The wash-out may be due to the loss of a second messenger-mediated mechanism linking the receptor to the response. The decrease in resting membrane conductance suggests that this second messenger may be required to maintain DBC glutamate channels in an open state in the absence of the receptor ligand.
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Vollum Institute for Advanced Biomedical Research, Oregon Health Sciences University, Portland 97201.
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D000818:Animals; D005971:Glutamates / Q000494:pharmacology* / Q000502:physiology; D018698:Glutamic Acid; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects*; D010786:Photoreceptor Cells / Q000378:metabolism / Q000502:physiology*; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D014562:Caudata / Q000502:physiology*
D005971:Glutamates; D018698:Glutamic Acid