[Effect of presynaptic neurotoxin notechis II-5 from tiger snake venom on the motor nerve endings of mice].
The neurotoxin notechis II-5 (N-II-5) from tiger snake venom (Notechis scutatus) induces three-phasic changes in miniature end-plate potential (MEPP) frequency recorded in the mouse diaphragm muscle: an initial fall of frequency followed by increase and decrease in MEPP frequency up to complete blockade. The effect of N-II-5 was enhanced with rising of the solution temperature from 20 to 30 and 35 degrees C. Removal of Ca2+ from the solution prevented the presynaptic effect of N-II-5. After washing out of the muscle from N-II-5 with Ca-free solution, addition of Ca2+ to the solution provoked the development of the effect typical of the effect of typical of the toxin. In the presence of N-II-5 an increase in K+ concentration in the solution up to 20 mM did not result in a sharp rise of MEPP frequency characteristic of depolarized nerve terminals. The agents that raise Ca2+ axoplasmic concentration not on account of depolarization of nerve terminals (hypertonic solution, ionofor A23187) preserved the capacity for increasing MEPP frequecy. It is suggested that the presynaptic effect of N-II-5 is related to its phospholipase activity and can be explained by disturbance of the activity of release sites rather than by depletion of transmitter stores.
D000200:Action Potentials; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D003470:Culture Media; D003964:Diaphragm / Q000294:innervation; D004546:Elapid Venoms / Q000494:pharmacology*; D051379:Mice; D009045:Motor Endplate / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology*; D010740:Phospholipases / Q000378:metabolism
D003470:Culture Media; D004546:Elapid Venoms; D009498:Neurotoxins; D000001:Calcimycin; D010740:Phospholipases; D002118:Calcium
Deĭstvie presinapticheskogo neíroktoksina notekhisa II-5 iz iada tigrovoĭ zmei na dvigatel'nye nervnye okonchaniia myshi.