CONICET | Buscador de Institutos y Recursos Humanos

Muscarinic toxins selective for muscarinic receptor subtypes.  Muscarinic toxins from Mamba venoms There are four species: Dendroaspis angusticeps (Eastern green mamba), D. viridis (Western green mamba), D. polylepis (black mamba), and D. jamesonii (Jameson´s mamba). The mamba venoms are very complex. By a combination of capillary electrophoresis and mass spectrometry, 70 peptides in the molecular weight range 6,000 to 9,000 were detected in the venom of D. polylepis (Perkins et al, 1993) and 83 in D. jamesonii kaimosae (Perkins and Tomer, 1995). They should elute in fraction III (Fig, 2A). D. angusticeps venom is less lethal than the venom of the other mambas, LD50 (i.v. or i.p). for D. angusticeps venom is 1-3 µg/ g mouse , 0.3-0.6 µg/g for D. polylepis, 0.3-0.7 µg/g for D. viridis and 0.3-0.9 µg/g D. jamesonii. The higher lethality is probably due to presence of large amounts of a-neurotoxins having LD50 in the range of 0.05-0.15 µg/g mouse. The black mamba is one of the world´s deadlest snakes. For example, one hospital in South Africa received seven patients bitten by D. polylepis and all of them died. The Indian cobra Naja naja has a more potent venom with an LD50 i.v. of 0.2 µg/g, but with a much lower mortality. The lack of correlation between human mortality and mouse lethal dose probably indicates that the black mamba injects much more venom than the cobra (Harvey et al., 1984, review). Synergism is typical for mamba venoms and for many other venoms. The most lethal constituents of D. angusticeps venom are a- and ∂-dendrotoxin, (LD50 i.v 23 and 15 µg/g mouse, respectively; Joubert and Taljaard, 1980). The dendrotoxin content is about 10 %, but the venom with an LD50 i,v. of 1-3 µg/g mouse is much more lethal than any of its most toxic constituents. For instance, dendrotoxins and fasciculins act in synergism by increasing the level of acetylcholine, dendrotoxins by increasing the release and fasciculins by inhibiting the breakdown.