Dual effect of glutamate and aspartate on the on-center bipolar cell in the carp retina.

In on-center bipolar cells of the carp retina, glutamate and aspartate applied extracellularly by pressure injection produced hyperpolarizing potential changes. These responses were not blocked by Co2+. Examination of reversal potentials revealed two different conductance changes. One of them appears to be an increase in K+ and/or Cl- conductance and the other a decrease in Na+ conductance. The results are discussed with relation to the difference in ionic mechanisms of cone and rod inputs.