Using mice infected with coxsackie B-3 virus （CVB3） as a viral myocarditis model

we observed the inhibitory effect of Astragalus membranaceus （AM） on CVB3-RNA replication in myocardial tissue of mice by RNA-RNA in situ hybridization with negative-strand RNA Probes labelled with ￣（35）S and quantitative imaging analysis of positive signals. The mechanism of its effect on CVB3-RNA replication has been investigated by detection of beta-interferon （β-IFN） as well. Results showed that the copy numbers of CVB3-RNA as well as the histologic scores （necrosis） in myocardial tissues of infected-AM treated mice were significantly lower than those in infected and normal saline treated mice

suggesting that AM could inhibit the replication of CVB3-RVA

but its effect on CVB3-RNA replication had no correlation with induction of β-IFN.