Intracellular calcium concentration changes initiated by N-methyl-D-aspartic acid receptors in retinal horizontal cells.

Intracellular calcium concentration changes initiated by N-methyl-D-aspartic acid receptors were studied in carp retinal horizontal cells. Fura-2 fluorescent calcium imaging showed that H1 subtype horizontal cells responded to exogenously applied N-methyl-D-aspartic acid with a transient intracellular free Ca(2+) ([Ca2+]i) increase that decayed to a sustained, but elevated level of [Ca(2+)]i. Contributions of different Ca(2+) flux pathways underlying the time course of this increase in [Ca(2+)]i were explored via experiment as well as via a computational model based on the biophysical properties of H1 cells. Intracellular calcium stores were suggested to play crucial role in the initial transient increase of [Ca(2+)]i.