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- Title
Activation of glutamate transporters in rods inhibits presynaptic calcium currents.
- Authors
KATALIN RABL; ERIC J. BRYSON
- Abstract
We found that L-glutamate (L-Glu) inhibits L-type Ca2+ currents (ICa) in rod photoreceptors. This inhibition was studied in isolated rods or rods in retinal slices from tiger salamander using perforated patch whole cell recordings and Cl--imaging techniques. Application of L-Glu inhibited ICa by ~20% at 0.1 mM and ~35% at 1 mM. L-Glu also produced an inward current that reversed around ECl. The metabotropic glutamate receptor (mGluR) agonists t-ADA (Group I), DCG-IV (Group II), and L-AP4 (Group III) had no effect on ICa. However, the glutamate transport inhibitor, TBOA (0.1 mM), prevented L-Glu from inhibiting ICa. D-aspartate (D-Asp), a glutamate transporter substrate, also inhibited ICa with significantly more inhibition at 1 mM than 0.1 mM. Using Cl- imaging, L-Glu (0.11 mM) and D-Asp (0.11 mM) were found to stimulate a Cl- efflux from terminals of isolated rods whereas the ionotropic glutamate receptor agonists NMDA, AMPA, and kainate and the mGluR agonist, 1S,3R-ACPD, did not. Glutamate-evoked Cl- effluxes were blocked by the glutamate transport inhibitors TBOA and DHKA. Cl- efflux inhibits Ca2+ channel activity in rod terminals (Thoreson et al. (2000), Visual Neuroscience 17, 197).
- Subjects
PHOTORECEPTORS; EXTRACELLULAR matrix; PHOTOBIOLOGY; RETINA; TIGER salamander
- Publication
Visual Neuroscience, 2003, Vol 20, Issue 5, p557
- ISSN
0952-5238
- Publication type
Article
- DOI
10.1017/s0952523803205095