ABSTRACT
We studied the mechanism of nitric oxide (NO) toxicity in cultured rat spinal motoneurons. Treatment with the NO donor NOC-18 (NOC) resulted in slow motoneuron death, ending in apoptosis. The observed motoneuron death was completely prevented by hemoglobin. Treatment with inhibitors of the known intracellular targets of NO, soluble guanylate cyclase, polyADP-ribose polymerase (PARP) and superoxide, did not result in any significant protection against NOC-induced motoneuron death. ATP levels were reduced as soon as 3 h after the start of NOC treatment, suggesting a direct inhibition of cellular energy production. NOC toxicity could be blocked by the general voltage-gated calcium channel blocker cobalt, but not by specific blockers of various subtypes of calcium channels.
