Physiological and Pharmacological Characterization of Glutamate and GABA Receptors in the Retina

Physiological and Pharmacological Characterization of Glutamate and GABA Receptors in the Retina

<P> Glutamate and γ-aminobutyric acid (GABA) are major excitatory and inhibitory neurotransmitters in the vertebrate retina, respectively. Using the whole-cell patch clamp technique and a rapid solution changer, glutamate and GABA receptors have been extensively investigated in carp retina. Glutamate receptors on both horizontal and amacrine cells may be an AMPA preferring subtype, which predominantly consists of flop splice variants. GABA<SUB>A</SUB> and GABA<SUB>C</SUB> receptors coexist in bipolar cells and they both show significant desensitization. Kinetics analysis demonstrated that activation, deactivation and desensitization of the GABA<SUB>C</SUB> receptor-mediated response of these cells are overall slower than those of the GABA<SUB>A</SUB> response. Endogenous modulator Zn<SUP>2&#8290;</SUP> in the retina was found to differentially modulate the kinetic characteristics of the GABA<SUB>C</SUB> and GABA<SUB>A</SUB> responses.