Diisopropylphosphorofluoridate-induced Depression of Compound Action Potential of Frog Sciatic Nerve in vitro is Mediated Through the Inhibition of Cholinesterase Activity
✍ Scribed by S.B. Deshpande; P. Kumar; A.S. Sachan; S.N. Dube; S. Das Gupta
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 356 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0260-437X
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✦ Synopsis
Effect of diisopropylphosphorofiuoridate (DFP), an irreversible cholinesterase (ChE) inhibitor, on compound action potential (CAP) of sciatic nerve in vitro was examined. Further, the role of cholinesterase reactivator ( 1 acetyl-4-hydroxy imino methyl pyridinium bromide; SPK-3) in reversing DFP-induced changes was also evaluated. Diisopropylphosphorofiuoridate produced a dose-dependent depression of the CAP. A concentration as low as 0.01 p M DFP produced a 5% depression ( P < 0.05) and the maximal depression (30% of control) was observed with 1 pM. The SPK-3 (up to 10 p M ) had no effect on the CAP; SPK-3 (10 pM) antagonized the DFP-induced depression of the CAP partially but not after 1 p M DFP. However, the inhibitory concentration of DFP to produce 5070 of the maximal depression ( I C ~~, ) was 0.38 +-0.025 p M in the presence of SPK-3 (10 pM; n = 4), against 0.15 k 0.05 pM for DFP alone ( n = 7 ) . These tcs0 values were significantly different (P < 0.05, Student's 1-test). The DFP decreased nerve ChE activity by 41% in the absence of SPK-3 and by 31% in the presence of SPK-3. Although SPK-3 could not completely reactivate the inhibited enzyme, it seems reasonable to conclude that the DFP-induced depression of the action potential of sciatic nerve was mediated by inhibiting the ChE activity.