Fisetin decreases the duration of ictal-like discharges in mouse hippocampal slices

Abstract

There is an increasing interest in the biological and therapeutic effects of fisetin, a natural phenolic compound. Fisetin has affinity on some neuronal targets and may have the potential to modulate neuronal activity. In this study the effects of acute application of fisetin on synchronized events were evaluated electro-physiologically. Besides, interaction of fisetin with closely related channels were investigated in silico. Acute horizontal hippocampal slices were obtained from 32- to 36-day-old C57BL/6 mice. Extracellular field potentials were recorded from CA3 region of the hippocampus. Bath application of 4 aminopyridine (4AP, 100 µM) initiated ictal- and interictal-like synchronized epileptiform discharges in the brain slices. Fifty micromolar fisetin was applied to the recording chamber during the epileptiform activity. The duration and frequencies of both ictal-like and interictal-like activities were calculated from the electrophysiological records. Molecular docking was performed to reveal interaction of fisetin on GABA-A, NMDA, AMPA receptors, and HCN2 channel, which are neuronal structures directly involved in recorded activity. Although fisetin does not affect basal neuronal activity in brain slice, it reduced the duration of ictal-like discharges significantly. Molecular docking results indicated that fisetin has no effect on GABA-A, NMDA, and AMPA receptors. However, fisetin binds to the (5JON) HCN2 channel strongly with the binding energy of -7.66 kcal/mol. Reduction on the duration of 4AP-induced ictal-like discharges can be explained as HCN channels can cause an inhibitory effect via enhancing M-type K + channels which increase K outward currents.

Keywords: 4AP; Brain slice; Fisetin; HCN channels; Molecular docking.

Fig. 1

The molecular structure of fisetin

Fig. 2

Location of electrodes and field potential recordings samples from CA3 of hippocampus. A Position of recording electrodes. B The sample records of interictal- and ictal-like activities after 100 µM 4AP induced epileptiform discharges. C Ictal activities. D Interictal activity

Fig. 3

A Sample trace of ictal events 4AP induced (upper) and after fisetin application (below). B The duration and the frequencies of ictal and interictal activities. The duration of ictal events decreases after fisetin application. There are significant reduction only in the durations of the ictal activities after fisetin application (p < 0.05, n = 10)

Fig. 4

The binding site and molecular position of fisetin to NMDA receptor (the views of the 3D reconstruction of NMDA receptor-fisetin (colored by red) and ifenprodil (colored by blue) complex (PDBID:5B3J)

Fig. 5

The binding site and molecular position of fisetin to GABA-A receptor (the views of the 3D reconstruction of GABA-A receptor-fisetin (colored by red) and bicuculline (colored by blue) complex (PDBID:6D6T)

Fig. 6

The binding site and molecular position of fisetin to AMPA receptor (the views of the 3D reconstruction of AMPA receptor-fisetin (colored by red) and perampanel (colored by blue) complex (PDBID:7LEP)

Fig. 7

The binding site and molecular position of fisetin to HCN2 receptor