Indian red scorpion (Mesobuthus tamulus concanesis, Pocock) venom prolongs repolarization time and refractoriness of the compound action potential of frog sciatic nerve in vitro through calcium dependent mechanism.
Indian J Exp Biol
;
1998 Nov; 36(11): 1108-13
Article
in English
| IMSEAR
| ID: sea-60993
ABSTRACT
Effects of Indian red scorpion (M. tamulus concanesis; MBT) venom on the compound action potential (CAP) of sciatic nerve in vitro were examined. MBT venom (0.1-6.0 micrograms/ml) prolonged the repolarization time and refractory period of the CAP in a concentration-dependent manner with maximal potentiation occurring at 6 micrograms/ml (about 100-200 times of the initial). At 1 microgram/ml of venom the prolongations were 40-50 times the initial durations and this concentration was used for subsequent experiments. Rise time, threshold, and conduction velocity of CAP were not altered by MBT venom (1 microgram/ml). In Ca(2+)-free medium, the venom-induced prolongations were only 2-6 times the initial response but addition of Ca2+ in the same medium then prolonged than by 50-70 times. The Ca2+ channel antagonists (nifedipine, 10 microM or Mg2+ ions, 5 mM) attenuated the venom (1 microgram/ml)-induced prolongation of repolarization time and refractory period. However, venom-induced prolongation of CAP responses were still significantly greater than the control in presence of these antagonists. The results indicate that MBT venom-induced increases in repolarization time and refractory period of the action potential greatly depend upon the presence of Ca2+ ions in the medium. The Ca2+ influx was through the L-type of Ca2+ channels.
Full text:
Available
Index:
IMSEAR (South-East Asia)
Main subject:
Ranidae
/
Sciatic Nerve
/
Scorpion Venoms
/
Action Potentials
/
Calcium Channel Blockers
/
Nifedipine
/
Calcium
/
Animals
Language:
English
Journal:
Indian J Exp Biol
Year:
1998
Type:
Article
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