Mitochondrial involvement in post-tetanic potentiation of synaptic transmission.

Posttetanic potentiation (PTP) is an essential aspect of synaptic transmission that arises from a persistent presynaptic [Ca2+]i following tetanic stimulation. At crayfish neuromuscular junctions, several inhibitors of mitochondrial Ca2+ uptake and release (tetraphenylphosphonium or TPP+, carbonyl cyanide m-chlorophenylhydrazone or CCCP, and ruthenium red) blocked PTP and the persistence of presynaptic residual [Ca2+]i, while endoplasmic reticulum (ER) Ca2+ pump inhibitors and release channel activators (thapsigargin, 2,5-di-(tert-butyl)-1,4-benzohydroquinone or BHQ, and caffeine) had no effects. PTP apparently results from the slow efflux of tetanically accumulated mitochondrial Ca2+.