OBJECTIVES: The purpose of this study is to investigate if the aqueous extract of the Chinese medicine Danggui-Shaoyao-San (DSS) can increase the plasma level of melatonin and enhance the function of the pineal gland of naturally aged rats.
METHODS: The rats were treated with DSS at doses of 3ml or same volume of distilled water by oral administration at 11 p.m. for three weeks. The plasma level of melatonin were measured by radioimmunoassay. The function of pineal gland were measured through three parameters: pineal beta adrenergic receptor binding investigated by [3H]DHA binding; pineal expression of NAT mRNA detected by real-time RT-PCR; phosphorylation of CREB (P-CREB) and total level of CREB (T-CREB) measured by western blot analysis.
RESULTS: DSS significantly increased melatonin level at night after oral administration for 3 weeks. By measurement of pineal [3H]DHA binding, it was found DSS improved the beta-adrenergic receptors binding in pineals. The stimulatory effect of DSS on the expression of NAT mRNA in the old rat pineal gland has been demonstrated in this study. Western blot analysis showed that DSS significantly increased phosphorylation of CREB.
CONCLUSIONS: Our results indicate that a downstream pathway for DSS induction of melatonin synthesis in the rat pineal gland acts via cyclic AMP-dependent cascade and transcription mechanism.