ATP-sensitive potassium channels counteract anoxia in neurones of the substantia nigra.

The ATP-sensitive potassium channel (KATP channel) is a unique ionophore in that it appears to reflect cell metabolism. In the brain, the highest density of binding sites for the KATP channel is the substantia nigra. To evaluate the role of the KATP channel in this key brain area for motor control, we used exposure to cyanide to lower intracellular ATP and thereby mimic anoxia and ischemia. Treatment with cyanide caused the activation of a potassium current in a sub-population of nigral neurones with distinct pharmacological and electrophysiological properties. The response to cyanide was abolished by the sulphonylurea tolbutamide, a potent blocker of the KATP channel. These results suggest that in the substantia nigra, the KATP channel plays a pivotal role in normal mechanisms of neuronal homeostasis in response to anoxia and ischaemia. The significance of these findings for our understanding of the cellular mechanisms in Parkinsonian degeneration is discussed.