Computational Insights into The Neuroprotective Action of
Riluzole on 3-Acetylpyridine-Induced Ataxia in Rats
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* Corresponding Address: P.O.Box: 81746-73441, Department of Biomedical Engineering, School of Engineering, University of Isfahan, Isfahan, Iran
Email: edrisi@eng.ui.ac.ir
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Abstract
2EMHFWLYHIntra-peritoneal administration of riluzole has been shown to preserve the -ebellar ataxia induced by 3-acetylpyridine (3-AP). However, the exact mechanism(s) by which riluzole restores the normal electrophysiological properties of Purkinje neurons is not completely understood. Changes in the conductance of several ion channels, includ-ing the BK channels, have been proposed as a neuro protective target of riluzole. In this study, the possible cellular effects of riluzole on Purkinje cells from 3-AP-induced ataxic rats that could be responsible for its neuro protective action have been investigated by computer simulations.
0DWHULDOVDQG0HWKRGV This is a computational stimulation study. The simulation
envi-activity of Purkinje cells without concerns about its other effects and interfering param-eters in the experiments. Simulations were performed in the NEURON environment
(Ver-sion 7.1) in a time step of 25 μs; analyses were conducted using MATLAB r2010a (The
Mathworks). Data were given as mean ± SEM. Statistical analyses were performed by the
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channel current, as suggested by previous experimental studies, should not be consid-ered as the only possible target for the neuro protective effects of riluzole to restore the
&RQFOXVLRQChanges in the conductance of several potassium channels, including
volt-age-gated potassium (Kv1, Kv4) and big Ca2+-activated K+ (BK) channels may be
respon-properties of Purkinje cells in a rat model of ataxia.
Keywords: Ataxia, Riluzole, Potassium Channels, Neuroprotection, Computer Simulation
Cell Journal(Yakhteh), Vol 15, No 2, Summer 2013, Pages: 98- 107
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Materials and Methods
Computer simulations
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mum conductance of the resurgent Na current was VOLJKWO\LQFUHDVHGIURPP6FP2WRP6FP2; the diameter and length of soma were both increased IURPPWRP
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Electrophysiological assessment
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Results
Comparison of the electrophysiological charac-teristics of control and ataxic Purkinje neurons
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Fig 3: Bursting activity of a real ataxic Purkinje neuron. A. Fast time scale and B.Slow time scale.
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Table 1: Electrophysiological characteristics of real and simulated Purkinje cells under normal and ataxia conditions
Simulated ataxic purkinje cell Simulated normal
purkinje cell Purkinje cells from
ataxic rats Normal purkinje
cell Electrophysiological
parameters
Frequency (Hz)
AP amplitude (mV)
AHP amplitude (mV)
AP duration (ms)
Neuroprotective effects of riluzole on ataxic Purkinje neurons
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A
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A
B
)LJ6LPXODWHGVSRQWDQHRXVWRQLF¿ULQJRIWKH3XUNLQMH cell in A. Normal, B. Ataxia, and C. Riluzole-treated ataxia conditions.
6LPXOWDQHRXVFKDQJHLQ%.DQG.YFRQGXFW ances were not the only possible alterations in WKHHOHFWURSK\VLRORJLFDOSURSHUWLHVRIWKHDWD[LF 3XUNLQMHFHOOVWKDWFRXOGUHVWRUHWKHLU¿ULQJDFWLY LW\$QRWKHUSRVVLEOHPHFKDQLVPIRUWKHULOX]ROH LQGXFHG QHXUR SURWHFWLRQ DJDLQVW $3 WR[LFLW\ could be through a combination of changes in WKH FRQGXFWDQFHV RI .Y DQG .Y FKDQQHOV VR WKDWDGHFUHDVHLQWKHFRQGXFWDQFHRI.Y channels could also simulate the neuro protec WLYH HIIHFW RI ULOX]ROH RQ WKH PRGHOHG 3XUNLQMH FHOOV ZKHQ DFFRPSDQLHG E\ D LQFUHDVH LQ WKHFRQGXFWDQFHRI.YFKDQQHOV$VLPLODUUHVXOW ZDV DOVR DFKLHYHG E\ DQG LQFUHDVHV LQ WKHFRQGXFWDQFHRI.YDQG,KFKDQQHOVUHVSHF WLYHO\,QDGGLWLRQDPLQLPXPLQFUHDVHRI%. FKDQQHODQG,KFKDQQHOUHVWRUHGWKH¿ULQJ DFWLYLW\RIWKHPRGHOHGDWD[LF3XUNLQMHFHOOWRWKH normal condition.
+RZHYHU FKDQJHV LQ WKH FRQGXFWDQFH RI .Y and Ih channels did not restore the electrophysi RORJLFDOSURSHUWLHVRIWKHPRGHOHGDWD[LF3XUNLQMH cell to the normal condition.
7KHUHDUHDOVRVHYHUDOWKUHHFKDQQHOFRPELQD WLRQVRIFKDQJHVLQFRQGXFWDQFHZKLFKKDYHUHVXOW HGLQUHVWRULQJ¿ULQJDFWLYLW\RIWKHPRGHO3XUNLQMH cell. Table 2 summaries these combinations. B
C
Table 2: Summary of the results, which demonstrate the minimum changes in the conductance of GLIIHUHQWFKDQQHOVZKLFKPD\UHVWRUHWKH¿ULQJDFWLYLW\RIDWD[LF3XUNLQMHFHOOVWRQRUPDO
Ability to restore electrophysiological characteristics of ataxia to normal conditions
Channel modulation
No
Kv4 inhibition
No
BK stimulation
No
Kv1 stimulation
No
Ih stimulation
<HV Kv4 inhibition (10%) and BK stimulation (75%)
<HV Kv4 inhibition (10%) and Kv1 stimulation (90%)
<HV Kv4 (10%) inhibition, Kv1 (40%) and BK (40%)
stimulation
<HV Ih (40%) and BK (80%) stimulation
<HV Ih (40%) and Kv1 (80%) stimulation
<HV Ih (40%), Kv1 (40%) and BK (40%) stimulation
Discussion
In the present study we discussed the possible FHOOXODUPHFKDQLVPVRIDFWLRQRIULOX]ROHDVDQHX URSURWHFWLYHDJHQW$VLPXODWLRQHQYLURQPHQWZDV XVHGWRHYDOXDWHWKHFRQWULEXWLRQVRIGLIIHUHQWLRQ FKDQQHOV SUHYLRXVO\ SURSRVHG WR GHWHU PLQH LI FKDQJHV LQ WKHLU FRQGXFWDQFHV FRXOG H[ plain restoration of the electrophysiological prop erties of these cells.
The simulation findings suggested that modu lation of the conductance of each of the pro posed channels alone could not be responsible IRU WKH HOHFWURSK\VLRORJLFDO HIIHFWV RI ULOX]ROH RQDWD[LFFHOOV+RZHYHUVHYHUDOFRPELQDWLRQDO effects on two or three of the proposed channels VLPXODWHGWKHREVHUYHGQHXURSURWHFWLYHHIIHFWV RI ULOX]ROH RQ WKH ILULQJ DFWLYLW\ RI 3XUNLQMH cells. These proposed combinations consisted RI.YLQKLELWLRQDQG%.DFWLYDWLRQ.YLQKL ELWLRQDQG.YDFWLYDWLRQ.YLQKLELWLRQZLWK .YDQG%.DFWLYDWLRQ,KDQG%.DFWLYDWLRQ ,KDQG.YDFWLYDWLRQRU,K.YDQG%.DFWL YDWLRQ
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+RZHYHU QR H[SHULPHQWDO HYLGHQFH KDV EHHQ found in the literature for an increase in Ih chan QHO FXUUHQW LQ WKH SUHVHQFH RI ULOX]ROH 7KHUH IRUH LW LV PRVW SRVVLEOH WKDW D FRPELQDWLRQ RI VHYHUDOLRQLFFKDQQHOVLQFOXGLQJ.Y.YDQG %.DUHUHVSRQVLEOHIRUWKHQHXURSURWHFWLYHHI IHFWVRIULOX]ROH
)LJXUHVDQGVXPPDUL]HWKHVLPXODWHGDQG UHDOHIIHFWRIULOX]ROHRQWKHHOHFWURSK\VLRORJLFDO FKDUDFWHULVWLFVRI3XUNLQMHQHXURQVUHVSHFWLYHO\
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Fig 13: Real effects of riluzole on the electrophysiological characteristics of Purkinje neurons, including A.Input resistance, B.Resting membrane potential, C.AHP amplitude, D. Action potential (AP) amplitude and E. AP half width (1).
,Q FRPSDULVRQ ZLWK FRQWURO DQG ULOX]ROH FR WUHDWPHQWFRQGLWLRQVWKHLQSXWUHVLVWDQFHRI3&V VLJQL¿FDQWO\LPSURYHG%RWKUHVWLQJPHPEUDQH SRWHQWLDOV RI 3&V UHPDLQHG XQFKDQJHG KRZ HYHUWKHUHZDVDVLJQLILFDQWGHFUHDVHLQWKH$3V amplitude and a significant increase in its dura WLRQLQDWD[LFUDWV%RWKSDUDPHWHUVDOPRVWUH WXUQHGWRFRQWUROYDOXHVLQWKHULOX]ROHFRWUHDW ed groups. The results were almost the same in WKHUHDODQGVLPXODWHGHIIHFWVRIULOX]ROHRQWKH HOHFWURSK\VLRORJLFDOFKDUDFWHULVWLFVRI3XUNLQMH neurons.
The results of this study may be used in fu WXUH H[SHULPHQWV WR GHWHUPLQH PRUH H[DFWO\ WKH PHFKDQLVPV E\ ZKLFK ULOX]ROH UHVWRUHV WKH electrophysiological properties of neuronal cells against normal conditions.
Conclusion
HIIHFWRIULOX]ROHDVREVHUYHGLQWKHH[SHULPHQWDO VWXGLHV7KHUHIRUHLWVHHPHGWKDWFKDQJHVLQWKH FRQGXFWDQFH RI VHYHUDO SRWDVVLXP FKDQQHOV LQ FOXGLQJ.Y.YDQG%.PLJKWEHUHVSRQVLEOH IRU WKH QHXURSURWHFWLYH HIIHFW RI ULOX]ROH DJDLQVW $3LQGXFHGDOWHUDWLRQVLQWKHHOHFWURSK\VLRORJL FDO FKDUDFWHULVWLFV RI 3XUNLQMH QHXURQV LQ D UDW PRGHORIDWD[LD
Acknowledgments
7KHDXWKRUVZRXOGDOVROLNHWRH[SUHVVWKHLUDS SUHFLDWLRQWRWKH1HXURVFLHQFH5HVHDUFK&HQWHURI 6KDKLG %HKHVKWL 8QLYHUVLW\ RI 0HGLFDO 6FLHQFHV IRUWKHLUDVVLVWDQFHLQGDWDFROOHFWLRQDQGWKH8QL YHUVLW\RI,VIDKDQIRUWKHLU¿QDQFLDOVXSSRUW7KLV ZRUNZDVGRQHDVD0DVWHU¶VWKHVLVDWWKH8QLYHU VLW\RI,VIDKDQ7KHUHLVQRFRQÀLFWRILQWHUHVWLQ this article.
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