PD-85639 is a voltage-gated sodium (Na+) channel blocker (75% in 10 min & >95% in 25 min blockage of Na+ current by 25 μM PD85,639; whole-cell patch clamp using primary rat brain neurons) that is shown to target rat brain Nav1.2 with simultaneous high- and low-affinity modes of binding (EC50 = 56 nM/40% & 20 μM/60% at pH 9.0, 5 nM/28% & 3 μM/72% at pH 7.4, against 2 nM [3H]-PD85,639 for binding rat brain synaptosomes; EC50 = 17 nM/39% & 10 μM/61% using at pH 9.0 using rat brain synaptosome membranes) and a fast kinetic (t1/2 = 1.2 at 4°C, <0.5 min at 25°C), competitive against the local anesthetic Na+ channel blockers tetracaine, bupivacaine, and mepivacaine, as well as Na+ channel activators veratridine and batrachotoxin (K1 = 0.26 μM against 5 nM [3H]-BTX for binding rat neocrotical membranes).