Background: The contribution of histamine (H1) receptors inhibitory and/or β-adrenoceptors stimulatory mechanisms in the relaxant property of Ferula assa-foetida. (F. asafoetida) was examined in the present study. Methods: We evaluated the effect of three concentrations of F. asafoetida extract (2.5, 5, and 10 mg/mL), a muscarinic receptors antagonist, and saline on methacholine concentration-response curve in tracheal smooth muscles incubated with β-adrenergic and histamine (H1) (group 1), and only β-adrenergic (group 2) receptors antagonists. Results: EC50 values in the presence of atropine, extract (5 and 10 mg/mL) and maximum responses to methacholine due to the 10 mg/mL extract in both groups and 5 mg/mL extract in group 1 were higher than saline (P < 0.0001, P = 0.0477, and P = 0.0008 in group 1 and P < 0.0001, P = 0.0438, and P = 0.0107 in group 2 for atropine, 5 and 10 mg/mL extract, respectively). Values of concentration ratio minus one (CR-1), in the presence of extracts were lower than atropine in both groups (P = 0.0339 for high extract concentration in group 1 and P < 0.0001 for other extract concentrations in both groups). Conclusion: Histamine (H1) receptor blockade affects muscarinic receptors inhibitory property of F. asafoetida in tracheal smooth muscle
Receptors, Muscarinic

OBJECTIVE: To investigate the effect of hydro-ethanolic extract of Zataria multiflora (Z. multiflora) on endothelin level, total and differential white blood cells (WBC) count of sensitized guinea pigs. METHODS: Five groups of guinea pigs sensitized to ovalbumin (OA) were given drinking water alone (group S), drinking water containing three concentrations of Z. multiflora (0.2, 0.4 and 0.8 mg/mL as groups S+Z1, S+Z2 and S+Z3) and dexamethasone (group S+D), n=6 for each group. The endothelin levels as well as total and differential WBC count in blood of sensitized and control guinea pigs were evaluated using enzyme linked immunosorbent assay method, and hemocytometer and Wright-Giemsa's staining of blood sample smear respectively. RESULTS: Blood endothelin levels, total and most differential WBC count were increased but lymphocytes decreased in sensitized animals compared to controls (allP <0.01). In groups S+D, S+Z2 and S+Z3 endothelin level, total and differential WBC counts were significantly improved compared with group S (P <0.01). Although, all measured parameters in group S+Z1 was lower than group S+D (P <0.01), some parameters in group S+Z3 were greater than in group S+D (P <0.05 toP <0.01). CONCLUSION The results showed an anti-inflammatory effect of Z. multiflora extract in sensitized guinea pigs, which may suggest a therapeutic potential for the plant on asthma.