Abstract: Aim To investigate the effect of ligustrazine on pulmonary arterial pressure,thromboxane A₂(TXA₂)and prostacyclin(PGI₂)in chronic hypoxic hypercapnic rats.Methods Thirty rats were randomly divided into control group(A),hypoxic hypercapnic group(B)and hypoxic hypercapnia+ligustrazine (lig)group(C).Results The mPAP in group B was significantly higher than that in group A(P<0.01)and group C(P<0.01).Differences of mCAP among groups were not significant (P>0.05);The specific value of WA/TA(vessel wall area/total area) and SMC (the density of medial smooth muscle cells)were significantly higher in group B than that in group A(P<0.01)and group C(P<0.01).Electron microscopy showed the proliferation of medial smooth muscle cells and collageous fibers of pulmonary ar-terioles in ratsof group B and ligustrazine could invert the changes mentioned above.Plasma TXB₂ concentration and TXB_2/6-keto-PGF 1αwere significantly higher in ratsof group B than that of group A(P<0.01)and group C (P<0.01).Differences of 6-keto-PGF_1α were not significant among groups(P>0.05).Conclusion Ligustrazine can inhibit pulmonary hyper-tension and structural remodeling of pulmonary artery in chronic hypoxic hypercapnic rats by inhibiting synthesis of TXA₂.

Key words: ligustrazine, anoxia, hypercapnia, hypertension, pulmonary, thromboxane A₂, prostacyclin