Korean J Physiol Pharmacol.  2018 May;22(3):249-255. 10.4196/kjpp.2018.22.3.249.

Echinacoside, an active constituent of Herba Cistanche, suppresses epileptiform activity in hippocampal CA3 pyramidal neurons

• Lu CW
• Huang SK
• Lin TY
• Wang SJ

• KMID: 2410089
• DOI: http://doi.org/10.4196/kjpp.2018.22.3.249

Abstract

Echinacoside, an active compound in the herb Herba Cistanche, has been reported to inhibit glutamate release. In this study, we investigated the effects of echinacoside on spontaneous excitatory synaptic transmission changes induced by 4-aminopyridine (4-AP), by using the in vitro rat hippocampal slice technique and whole-cell patch clamp recordings from CA3 pyramidal neurons. Perfusion with echinacoside significantly suppressed the 4-AP-induced epileptiform activity in a concentration-dependent manner. Echinacoside reduced 4-AP-induced increase in frequency of spontaneous excitatory postsynaptic currents (sEPSCs) but it did not affect the amplitude of sEPSCs or glutamate-activated currents, implicating a presynaptic mechanism of action. Echinacoside also potently blocked sustained repetitive firing, which is a basic mechanism of antiepileptic drugs. These results suggest that echinacoside exerts an antiepileptic effect on hippocampal CA3 pyramidal neurons by simultaneously decreasing glutamate release and blocking abnormal firing synchronization. Accordingly, our study provides experimental evidence that echinacoside may represent an effective pharmacological agent for treating epilepsy.

Keyword

4-aminopyridine; Antiepileptic activity; Echinacoside; Excitatory synaptic activity; Hippocampus

MeSH Terms

4-Aminopyridine
Animals
Anticonvulsants
Cistanche*
Epilepsy
Excitatory Postsynaptic Potentials
Fires
Glutamic Acid
Hippocampus
In Vitro Techniques
Perfusion
Pyramidal Cells*
Rats
Synaptic Transmission
4-Aminopyridine
Anticonvulsants
Glutamic Acid

Figure

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  Fig. 1 Effect of echinacoside on the epileptiform activity induced by 4-AP in CA3 pyramidal neurons in rat hippocampal slices.(A) Representative current clamp recordings in control, echinacoside (20 µM), 4-AP (1 mM), and 4-AP (1 mM)+echinacoside (20 µM). 4-AP was applied for 10 min to induce epileptiform activity. Echinacoside was added 10 min after the application of 4-AP. (B) Normalized dose-response relationship of the effect of echinacoside on epileptiform activity induced by 4-AP (n=3-6). **p<0.01, ***p<0.001 vs. control group.

• 

  Fig. 2 Effect of echinacoside on spontaneous excitatory postsynaptic potentials (sEPSCs) induced by 4-AP in hippocampal CA3 pyramidal neurons.(A) Representative voltage clamp recordings in control, echinacoside (20 µM), 4-AP (1 mM), and 4-AP (1 mM)+echinacoside (20 µM). Echinacoside was added 10 min after the application of 4-AP. (B, C) Cumulative probability plots of sEPSCs frequency and amplitude, respectively. Each result represents mean values from 5 neurons. ***p<0.001 vs. control group. *p<0.05 vs. the 4-AP-treated group.

• 

  Fig. 3 Effect of echinacoside on miniature excitatory postsynaptic potentials (mEPSCs) in hippocampal CA3 pyramidal neurons.(A) Representative voltage clamp recordings from neurons before (control) and after echinacoside (20 µM) application for 10 min. mEPSCs recorded in the presence of TTX. (B, C) Cumulative probability plots of mEPSCs frequency and amplitude, respectively. Each result represents mean values from 5 neurons. ***p<0.001 vs. control group.

• 

  Fig. 4 Effect of echinacoside on glutamate-evoked postsynaptic currents (IGlu) in hippocampal CA3 pyramidal neurons.Superfusion of 100 µM glutamate for 10 s evoked an inward current. (A) Typical IGlu traces recorded from a CA3 pyramidal neuron before (control) and after echinacoside (20 µM) application for 10 min. (B) Summary data (n=5) showing mean values of peak IGlu in the absence (control) and presence of 20 µM echinacoside.

• 

  Fig. 5 Effect of echinacoside on sustained repetitive firing in hippocampal CA3 pyramidal neurons.(A) Representative current clamp recordings of action potential induced by depolarizing current pulses (500 ms; 1 nA) from neurons before (control) and after echinacoside (20 µM) application for 10 min. (B) Summary data (n=7) showing mean values of action potential frequency in the absence (control) and presence of 20 µM echinacoside. ***p<0.001 vs. control group.

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