Format

Send to

Choose Destination
See comment in PubMed Commons below
J Neurosci. 1999 Apr 15;19(8):2938-44.

The metabotropic receptor mGluR6 may signal through G(o), but not phosphodiesterase, in retinal bipolar cells.

Author information

1
Departments of Ophthalmology and Visual Science, and Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

Abstract

Bipolar cells are retinal interneurons that receive synaptic input from photoreceptors. Glutamate, the photoreceptor transmitter, hyperpolarizes On bipolar cells by closing nonselective cation channels, an effect mediated by the metabotropic receptor mGluR6. Previous studies of mGluR6 transduction have suggested that the receptor couples to a phosphodiesterase (PDE) that preferentially hydrolyzes cGMP, and that cGMP directly gates the nonselective cation channel. This hypothesis was tested by dialyzing On bipolar cells with nonhydrolyzable analogs of cGMP. Whole-cell recordings were obtained from On bipolar cells in slices of larval tiger salamander retina. Surprisingly, On bipolar cells dialyzed with 8-(4-chlorophenylthio)-cyclic GMP (8-pCPT-cGMP), or 8-bromo-cyclic GMP (8-Br-cGMP) responded normally to glutamate or L-2-amino-4-phosphonobutyrate (L-APB). Response amplitudes and kinetics were not significantly altered compared with cells dialyzed with cGMP alone. Comparable results were obtained with the PDE inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) or with 8-pCPT-cGMP and IBMX together, indicating that PDE is not required for mGluR6 signal transduction. Addition of the G-protein subunit G(o)alpha to the pipette solution suppressed the cation current and occluded the glutamate response, whereas dialysis with G(i)alpha or with transducin Gbetagamma had no significant effect on either the cation current or the response. Dialysis of an antibody directed against G(o)alpha also reduced the glutamate response, indicating a functional role for endogenous G(o)alpha. These results indicate that mGluR6 may signal through G(o), rather than a transducin-like G-protein.

PMID:
10191311
[Indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Support Center