In vivo Detection of Changes in Membrane Potential in Rat Cortex by T2 mapping

Membrane potential is the crucial element of neuronal activation. We investigated the possibility of using MRI to detect the depolarization of membrane potential in rat cortex. To directly access brain cells, a craniotomy was performed to make a burr hole on the skull. T2 change in the exposed cortex was measured while depolarizing it by directly perfusing artificial cerebrospinal fluid of high potassium concentration. Our findings showed that T2 value of depolarized cortex increased by +2.7% at [K+] = 80 mM. This observation demonstrates that changes in membrane potential are detectable with MRI by T2 contrast in vivo.