NMDA-Receptor-Initiated Modulatory Effect on GABA Transporter Current: Experiment and Modelling

Whole cell recording was applied to investigated the modulatory effect of N-methyl-D-aspartate (NMDA) on gamma-aminobutyric acid (GABA) transporter current on enzymatically isolated horizontal cells of carp retina, and a model containing endoplasmic reticulum (ER) membrane process and plasma membrane process was constructed for quantitative analyses of the modulatory effect of NMDA and changes of intracellular Ca²⁺. The GABA transporter current elicited by GABA (1 mM) was decreased by pre-application of NMDA (0.1 mM). The suppressive effect could be attenuated when the intracellular Ca²⁺ store was depleted after the cell had been pre-incubated with 10 muM thapsigargin, a selective blocker of ER Ca²⁺-ATPase. The model analyses suggest that application of NMDA caused a transient release of Ca²⁺ from Ca²⁺ store, which was important for the NMDA modulation of GABA transporter.