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Anticonvulsant effect of FS‐1 subfraction isolated from roots of Delphinim denudatum on hippocampal pyramidal neurons
Author(s) -
Raza Mohsin,
Shaheen Farzana,
Choudhary M. I.,
Rahman Attaur,
Sombati Sompong,
Suria Amin,
Rafiq Azhar,
DeLorenzo R. J.
Publication year - 2003
Publication title -
phytotherapy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.019
H-Index - 129
eISSN - 1099-1573
pISSN - 0951-418X
DOI - 10.1002/ptr.1072
Subject(s) - depolarization , hyperpolarization (physics) , chemistry , hippocampal formation , anticonvulsant , membrane potential , electrophysiology , biophysics , voltage clamp , phenytoin , pharmacology , neuroscience , stereochemistry , epilepsy , medicine , biology , biochemistry , nuclear magnetic resonance spectroscopy
The effects were investigated of a partially purified subfraction (FS‐1) isolated from Delphinium denudatum on sustained repetitive firing (SRF) of cultured neonatal rat hippocampal pyramidal neurons. The blockade of sustained repetitive firing is one of the basic mechanisms of antiepileptic drugs at the cellular level. Using the whole cell current‐clamp technique, sustained repetitive firing was elicited in pyramidal neurons under study by a depolarizing pulse of 500 ms duration, 0.3 Hz and 0.1–0.6 nA current strength. FS‐1 (0.01–0.06 mg/mL) reduced the number of action potentials per pulse in a dose‐dependent manner until no action potentials were elicited for the remainder of the pulse. There was a corresponding use‐dependent reduction in amplitude and V max of action potentials. The V max of action potential 1 exhibited a dose‐dependent reduction. At a dose of 0.06 mg/mL FS‐1 reduced V max to 29%–38% and amplitude to 16%–20 % of the control values. The blockade of sustained repetitive firing by FS‐1 was reversed by hyperpolarization of the membrane potential (−65 to −75 mV) while depolarization of the membrane potential (−53mV to −48 mV) potentiated the block. The results suggest that FS‐1 blocks sustained repetitive firing in hippocampal neurons in a use‐dependent and voltage‐dependent manner similar to the prototype anticonvulsant drug, phenytoin. However, unlike phenytoin, which binds preferably to the inactive state, the compounds present in FS‐1 also interacted with the resting state of the Na + channels by reducing V max of action potential 1. The results indicate that the partially purified FS‐1 subfraction of Delphinium denudatum contains a potent anticonvulsant compound. Copyright © 2003 John Wiley & Sons, Ltd.