Mitochondrial Ca(2+) uptake is essential for synaptic plasticity in pain.

The increase of cytosolic free Ca(2+) (Ca(2+)) due to NMDA receptor activation is a key step for spinal cord synaptic plasticity by altering cellular signal transduction pathways. We focus on this plasticity as a cause of persistent pain. To provide a mechanism for these classic findings, we report that Ca(2+) does not trigger synaptic plasticity directly but must first enter into mitochondria. Interfering with mitochondrial Ca(2+) uptake during a Ca(2+) increase blocks induction of behavioral hyperalgesia and accompanying downstream cell signaling, with reduction of spinal long-term potentiation (LTP). Furthermore, reducing the accompanying mitochondrial superoxide levels lessens hyperalgesia and LTP induction. These results indicate that Ca(2+) requires downstream mitochondrial Ca(2+) uptake with consequent production of reactive oxygen species (ROS) for synaptic plasticity underlying chronic pain. These results suggest modifying mitochondrial Ca(2+) uptake and thus ROS as a type of chronic pain therapy that should also have broader biologic significance.