In recent decades natural biological products (including components of animals and plants) have increasingly been investigated to discover new drugs. In this study, different dendrotoxins from Eastern green mamba (Dendroaspis aungusticeps) venom were examined for their effects on neurotransmitter release in chicken biventer cervices nerve-muscle preparation using twitch tension recording technique. Twitches of the biventer cervices were evoked by stimulating the motor nerve at 0.1 Hz with pulses of 0.2 msec duration and a voltage of greater than that required to produce the maximum response. Twitches and contractures were recorded isotonically using polygraphs (Grass model 79 and Grass model 79B) and Grass FT03 force transducers. Alpha- and ?-dendrotoxin (10 ?g/ml ? 1.4 ?M) produced a significant augmentation in twitch amplitude, whereas ?- and ?-dendrotoxin did not appear to be effective at this concentration. These results were consistent with other reports using binding competition assays to demonstrate that ?- and ?-dendrotoxin are more potent than ?- and ?-dendrotoxin in their affinity for the binding sites of radiolabelled ? -dendrotoxin. Overall, it is concluded that the potency of different dendrotoxins are as follows: ?>?> ?>?.