Abstract: Objective To assess the relationship between protease-activated receptor 1 (PAR1) expression in the basilar artery
and cerebral vasospasm (CVS) in a rat model of subarachnoid hemorrhage (SAH). Methods Twenty-four SD rats were
randomized into normal control group, SAH 3-days group, SAH 5-days group and SAH 7-days group. Rat models of SAH
were established by two injections of blood into the cisterna magna and the behavioral changes of the rats were observed. The
basilar arteries were taken at 3, 5, or 7 days following the modeling for measuring the cross-sectional area of the basilar artery
and for immunohistochemical detection of PAR1 expression. Results The SAH model rats, especially those in SAH 3-days
group, presented with obvious neurological deficits, which was not found in the normal control group. CVS was not observed
in the normal control group but occurred in the SAH model rats, which showed reduced cross-sectional area of the basilar
artery and worsening spasm over time. The expression level of PAR1 tended to increase gradually in SAH 3-days, SAH 5-days
and SAH 7-days groups. Pearson correlation analysis showed an inverse correlation between the expression of PAR1 and the
cross-sectional area of the basilar artery (r=-0.779, P<0.01). Conclusions The expression of PAR1 increases significantly in rat
basilar artery wall following SAH in positive correlation with the severity of CVS, suggesting the role of thrombin in the
pathological process of CVS after SAH.