Effects of ligustrazine on the Ca2+ sensitivity in carotid artery smooth muscle of simulated weightlessness rats

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To study the effects of Ligustrazine on the Ca2+ sensitivity in carotid artery smooth muscle of simulated weightless-ness rats. Twenty-one female SD rats were divided into control group (CON), simulated weightlessness group (TS), simulated weightlessness plus Ligustrazine administration group (LTZ) (n=7). After 4 weeks, the contractile property and the Ca2+ sensitivity in carotid artery were measured. Furthermore, the effects of ML-7(a myosin light chain kinase specific inhibitor) on above mentioned parameters were recorded. Compared with CON group, the contractile force induced by phenylephrine (PHE) in TS group was increased by 25.14% (P<0.01). The force in LTZ group decreased by 13.46% (P<0.01) and increased by 8.30% compared with TS and CON group, respec-tively. After the artery rings were incubated with ML-7, the force in CON, TS and LTZ group were reduced by 8.84%, 16.24% (P<0.01) and 3.40%, respectively. Compared with CON group, the contractile force induced by KCl in TS group was increased by 40.46% (P<0.01). The force in LTZ group decreased by 18.80% and increased by 14.05% compared with TS and CON group, respectively. The force in CON, TS and LTZ group were reduced by 21.97% (P<0.05), 21.88% (P<0.01) and 10.84% by ML-7, respectively. Compared with CON group, the pD2[Ca2+] in TS group was increased by 10.03% (P<0.01). The pD2[Ca2+] in LTZ group was decreased by 7.01% (P<0.01) and increased by 2.32% compared with TS and CON group, respectively. The pD2[Ca2+] in CON, TS and LTZ group was reduced by 2.42%, 7.43% (P<0.01) and 2.51% by ML-7, respectively. The contraction of carotid artery is strength-ened in simulated weightlessness rats, it maybe results from the Ca2+ sensitivity of contractile proteins in smooth muscle increasing. Ligus-trazine can improve the contraction of carotid artery, reducing the Ca2+ sensitivity and inhibiting myosin light chain kinase may be involved in its mechanisms.