Zinc Modulation of Calcium-Permeable AMPA Receptors on Carp Retinal Horizontal Cells

Calcium-permeable AMPA receptors are proved to be expressed on carp retinal horizontal cells. However, the synaptic contribution and modulatory characteristics of these receptors in the synapses between cones and horizontal cells are not fully understood. In the present study, we used whole-cell patch clamp technique to test the functional contribution of calcium-permeable AMPA receptors and relevant zinc modulatory effect on these receptors. It is shown that application of 100 mu M pentobarbital (a selective blocker of calcium-impermeable AMPA receptors) slightly but significantly suppressed the current elicited by 3 mM glutamate. Furthermore, the co-application of 300 mu M zinc apparently inhibited the remaining calcium-permeable AMPA receptors. These results suggest that calcium-permeable AMPA receptors contribute a large portion to the cell's glutamate-current and zinc can down-regulate the function of these receptors.