Effects of amino acids on the isolated chicken retina, and on its response to glutamate stimulation.

Abstract

Abstract— The effect of a number of amino acids on the transparency and on the release of of [14C]glutamate from isolated chicken retinae charged with this compound was investigated. Also the effect of various amino acids on the response of the retina to stimulation with unlabelled glutamate, which causes an increase in transparency and a release of the label, was examined. In parallel experiments the effect of these same amino acids on the transparency and spreading depression (SD) was investigated in preparations consisting of the posterior part of the eye. A number of amino acids such as L‐leucine, L‐phenylalanine, L‐tryptophan, L‐lysine, L‐histidine, L‐arginine and others had little or no effect on these preparations. DL‐valine and DL‐homoserine caused an increase in transparency but no release of the label and did not affect the response to glutamate. Another group of amino acids comprising DL‐a‐alanine, L‐serine, L‐threonine, L‐proline and glycine also caused an increase in the transparency of the retina without a release of labelled glutamate, but prevented the increase in transparency resulting from glutamate stimulation without affecting the release of the label. A final group of amino acids which included L‐glutamic acid diethyl ester, DL‐a‐methyl glutamate, L‐glutamine, L‐asparagine, DL‐homocysteate and L‐cysteine caused a change in transparency of the retina accompanied by a release of the label; they prevented the change in transparency as well as the release of the label during stimulation by glutamate. Some amino acids, L‐serine, L‐threonine, DL‐a‐methyl glutamate, L‐asparagine, DL‐homocysteate and L‐cysteine, caused wrinkling and folding of the retinae which furthermore became opaque. Of the amino acids investigated, proline gave promise of being a practical antagonist to the action of glutamate on the retina.