ABSTRACT
Buthotus schach is one of the most dangerous scorpions in tropical part of Iran. The effects of its crude venom at 1, 3, 10 microg/mL and its obtained fractions by gel filtrations were investigated on neuromuscular transmission. CBC and MHD indirectly and directly stimulated preparations techniques were used to study their possible pre or post junctional activities. At 3 and 10 microg/ mL [not at 1 microg/mL], BS venom caused initiall increase in twitch height followed by blockage due to large contraction that responded gradually at the same time. Contracture responses to exogenous Ach [1-2 mM, 30 sec] and Carb [30-40 microM, 60 sec] in the presence of the venom were not increased which does show no anticholinstrease effects. Furthermore Contracture response to KC1 [20-40 mM, 30 sec] does changed exposure to venom in CBC preparations. On the other hand the effects of the venom in response to directly stimulated preparations was shallower than in indirect stimulated preparations. So in agreement with KCL response BS venom affects mostly prejunctionally to facilitate the neurotransmitter release rather than postjunctionally effects. To access bioactive components, seven fractions were collected by gel filtrations techniques. Among the fractions F[6], LD[50]=21 microg < F[4], LD[50]= 35.5 microg < Venom LD[50]= 84 microg per mice were more toxic respectively. Both fractions show the same effects but stronger than venom on twitch height responses in indirectly stimulated CBC preparations. Finally, according to our results venom as well as fractions F4 and F6 act mostly prejunctionally on Ach release. More attempt is carrying out to study their effects on ion channel activities