Ca2+-dependent kainate excitotoxicity in the chick embryonic neural retina ex vivo

The chick embryonic neural retina ex vivo has been singled out as a unique example of Cl--dependent/Ca2+-independent excitotoxicity. However, after continuous incubation with 100 muM kainate, we have demonstrated the susceptibility of the chick retina to Ca2+-mediated damage, which becomes apparent after 12 h of exposure to the agonist in the absence of Cl-. Of the 20.8% lactate dehydrogenase released after 24h incubation with kainate, some 11% is Cl--dependent and the rest (9.8%) is presumably Ca2+-dependent. Upon omission of both Cl- and Ca2+; a 5% residual toxicity can still be detected after 24h. This can be overcome by inclusion of EGTA in the incubation medium to neutralize Ca2+ released during incubation. A Ca2+-dependent toxicity mechanism is then operative in the embryonic chick retina ex vivo. NeuroReport 11:3855-38580 2000 Lippincott Williams & Wilkins.