This study sought to reveal the relationship between Snap-25 and tetramine poisoning in order to approach the mechanism of tetramine poisoning.The levels of Snap-25 mRNA in the brain tissues of poisoned SD rats were detected by RT-PCR method.After 1 hour of intoxication, the expression level of Snap-25 mRNA did not change in the rat brain. It increased at day 1 and reached its peak at day 3. The expression level of Snap-25 mRNA begain to descend at day 5, but it was still higher than that in the rat brain tissue of control group.In this study the expression of Snap-25 of rat poisoned by tetramine was not markedly increased in the early stage of poisoning, indicating that the symptoms of rat poisoned by tetramine are not induced by the changes of the Snap-25 level. The mechanism of high expression in Snap-25 mRNA probably involves the negative feedback of the body, which may increase the releasing of neurohumor and hence mitigate the symptoms of poisoning.