OPENING OF ATP-SENSITIVE POTASSIUM CHANNELS BY CROMAKALIM CONFERS TOLERANCE AGAINST CHEMICAL ISCHEMIA IN RAT NEURONAL CULTURES

The effect of opening and of blocking of ATP-sensitive potassium (K-AT P) channels on the short-term capacity of neurons to resist ischemia-r eperfusion-induced cell injury, was studied in a model of primary rat neuronal cultures, subjected to metabolic poisoning by iodoacetic acid (150 mu M, 150 min), followed by reperfusion (1 h). The metabolic poi soning resulted in a marked decrease in cellular ATP content (from 65. 3 +/- 13.4 to 21.6 +/- 11.7 nmole/mg protein), simulating an ischemia, or hypoxia-induced condition of energy crisis. The degree of neuronal damage was assessed by the trypan blue exclusion test. Exposure of th e neurons to the channel-opener cromakalim (10 mu M; 15 min), prior to the insult, induced resistance, which could be abolished by the speci fic channel blocker glibenclamide (2 mu M). Glibenclamide also abolish ed the protection acquired by preconditioning of the neurons with iodo acetate (IA; 100 mu M), the adenosine Al agonist N6-(R)-phenylisopropy ladenosine (R-PIA; 100 mu M), or with the protein kinase C (PKC) activ ator 1,2 dioctanoyl-rac-glycerol (DOG; 1 mu M), The results indicate t hat in the neurons, opening of the KATP channels confers protection ag ainst an ATP-depleting crisis, and suggest that the protective effects induced by adenosine and by activation of PKC, are mediated by the op ening of these channels. (C) 1998 Elsevier Science Ireland Ltd. All ri ghts reserved.