Coexistence and function of glutamate receptor subtypes in the horizontal cells of the tiger salamander retina.
Effects of the major glutamate receptor agonists, kainate (KA), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), quisqualate (QA), N-methyl-D-aspartate (NMDA), L-alpha-amino-4-phosphonobutyrate (L-AP4), and trans-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) on horizontal cells (HCs) were studied in superfused larval tiger salamander retina. 20 microM of KA, AMPA, and QA mimicked the action of 3 mM glutamate in the absence and presence of 1 mM Co2+. 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocked the actions of KA and AMPA, but not those of QA and glutamate, indicative of the existence of CNQX-resistant QA receptors in the tiger salamander HCs. Prolonged application of ACPD hyperpolarized the HCs and enhanced the light responses, probably by shifting the resting HC voltage (Er) to a more hyperpolarized position. It is possible that the KA, AMPA, and CNQX-resistant QA receptors are involved in mediating the postsynaptic light responses in HCs, and ACPD receptors are involved in sensitivity adjustment of the HC responses.
Yang
X L
XL
Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030.
Wu
S M
SM
D000818:Animals; D003623:Dark Adaptation; D004594:Electrophysiology; D005971:Glutamates / Q000494:pharmacology; D006571:Heterocyclic Compounds / Q000494:pharmacology; D008564:Membrane Potentials; D010775:Photic Stimulation; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000502:physiology*; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D014562:Caudata
D005971:Glutamates; D006571:Heterocyclic Compounds; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter