Effects of FK506 on long-term potentiation observed by optical imaging in organotypic hippocampal slice culture

Electrophysiological and biochemical assays were used to observe long-term changes in synaptic efficacy following electrical and/or pharmacological manipulation of synaptic function. We investigated the effects of FK506 on synaptic plasticity in organotypic hippocampal slice culture (OHSC) using optical imaging system. Hippocampal slices were prepared from 6-7 day-old rats using a tissue chopper and placed on a membrane insert. 18 hr after kainic acid (KA) treatment, significant delayed neuronal death which was quantified by propidium iodide, NeuN, and TUNEL staining was detected in CA3 area at 24 hr after KA treatment. The neuronal death was prevented significantly at 24 hr after 0.1 μM FK506 treatment. In the electrophysiology study, optical signals were observed by long-term potentiation (LTP) followed by the stimulation of the Schaffer collateral pathway. The improvement in amount of LTP was found in the FK506-treated group. These results suggest that FK506 may have a beneficial role in recovery of synaptic efficacy following KA-induced neuronal injury.