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(ATP)) channels on the short-term capacity of neurons to resist ischemia-reperfusion-induced cell injury, was studied in a model of primary rat neuronal cultures, subjected to metabolic poisoning by iodoacetic acid (150 microM, 150 min), followed by reperfusion (1 h). The metabolic poisoning 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 the neurons to the channel-opener cromakalim (10 microM; 15 min), prior to the insult, induced resistance, which could be abolished by the specific channel blocker glibenclamide (2 microM). Glibenclamide also abolished the protection acquired by preconditioning of the neurons with iodoacetate (IA; 100 microM), the adenosine A1 agonist N6-(R)-phenylisopropyladenosine (R-PIA; 100 microM), or with the protein kinase C (PKC) activator 1,2 dioctanoyl-rac-glycerol (DOG; 1 microM). The results indicate that in the neurons, opening of the K(ATP) channels confers protection against an ATP-depleting crisis, and suggest that the protective effects induced by adenosine and by activation of PKC, are mediated by the opening of these channels.