Ethnopharmacological relevance: Du Liang soft capsule (DL) is a traditional Chinese medicine for treating migraines; it is made from two Chinese herbs, including Ligusticum striatum DC., root; Angelica dahurica (Hoffin.) Benth. & Hook.f. ex Franch. & Sav., root. Aim of the study: In the present study, we aimed to elucidate the pharmacodynamic action of DL and its mechanism in an animal model of migraines induced by glyceryl trinitrate (GTN). Materials and methods: Sixty rats were randomly divided into six groups, including a normal control group, model control group, positive group (Sumatriptan 0.006 g kg(-1)), and three DL groups (0.44, 1.31 and 3.93 g kg(-1)). All rats were intragastrically treated with the corresponding treatment for 7 consecutive days, and they were subcutaneously injected with GTN (10 mg kg(-1)) 30 min after the last treatment, except in the normal control group. After model establishment, the behaviors of all rats, including head scratching, cage climbing, and the development of red ears were observed continuously by digital camera every 30 min for 3 h. Four hours after GTN treatment, all rats were anaesthetized and the blood and tissue samples were collected. Plasma calcitonin gene related to peptide (CGRP) and endothelin (ET) levels were measured using the radioimmunoassay method, and serum NO was determined by the colorimetric method. Afterwards, the brainstem tissues were dissected and washed with physiological saline, and divided evenly into two parts. One part was used to test the monoamine levels, including levels of 5-hydroxytuptamine (5-HT), norepinephrine (NE) and dopamine (DA), by the fluorometric method, and the other part was used to determine the nuclear factor kappaB (NF-kappa B) p65, nuclear c-fos, inducible nitric oxide synthase (iNOS), interleukin (IL)-1 beta (IL-1 beta), and cyclooxygenase-2 (COX-2) levels by Western blot analysis. Results: In the pharmacodynamic action assay, DL (1.31 and 3.93 g kg(-1)) greatly improved the abnormal behaviors of migraine rats, including head scratching and cage climbing, and the development of red ears. In the mechanism assay, compared with the control group, the plasma CGRP and serum NO levels and the brainstem 5 -HT, NE and DA levels in the DL administration groups were significantly decreased; and the plasma ET levels were remarkably increased. Moreover, down-regulation of NF-kappa B p65, c-fos and pro-inflammatory cytokines, including iNOS, IL-1 beta and COX-2 in the brainstem in the DL administration groups were observed by Western blot analysis. Conclusions: The above results suggested that DL has a therapeutic effect on migraines, and its mechanism may be related to adjusting the level of neurotransmitters and vasoactive substances, consequently relieving neurogenic inflammation.