Objective: To study the effects of extracts from Callicarpa nudiflora(ECN) leaves on platelet activation and to elucidate its mechanisms. Method: The 50 male SD rats were randomly divided into blank group

Yunnan Baiyao group (0.930 g·kg-1)

ECN low

medium and high dose groups (0.131

0.263

0.525 g·kg-1). All the rats were treated for 10 days. After treatment

the platelets of the rats in all groups were extracted

and microscale plate method was used to determine adenosine diphosphate (ADP)-induced platelet aggregation rate; enzyme linked immunosorbent assay (ELISA) was used to determine thromboxane B2(TXB2) and 5-serotonin (5-HT) levels in platelet as well as cyclic adenosine 5'-monophosphate (cAMP) release level in platelet. Furthermore

the effect of ECN on phosphatidylinositol-3-kinases (p-PI3K) protein expression levels was determined by using Western blot assay. Result: ECN enhanced ADP-induced platelet aggregation significantly (P<0.05)

and it could significantly promote TXB2 and 5-HT release (P<0.05). Furthermore

cAMP level in platelet was (3.074±0.538)

(3.340±0.265) nmol·L-1respectively in ECN low dose group and high dose group

lower than (3.795±0.586) nmol·L-1 in blank group (P<0.05)

and cAMP level in ECN medium dose group was (3.003±0.242) nmol·L-1

significantly lower than that in blank group (P<0.01). In Western blot assay

it was found that ECN could significantly increase p-PI3K kinase protein expression (P<0.01). Conclusion: Collectively

the data presented here demonstrated that ECN enhanced the development of platelet aggregation and amplification of platelet activation. These effects may be associated with its up-regulation on P2Y12 receptors.