Effects of 18β-glycyrrhetinic-acid on cerebral vasospasm following experimental subarachnoid hemorrhage in rats

Abstract

Objective To investigate the role of gap junction in the pathomechanism and treatment of cerebral vasospasm after experimental subarachnoid hemorrhage. Methods 120 Sprague Dawley rats were assigned randomly to four groups: control(n=30), sham group(n=30), operation group(n=30) and treatment group(n=30). Animals were killed on the 1st , 3rd , 5th, 7th and 14th day(n=6) respectively.The Sprague Dawley rat two-subarachnoid hemorrhage model was established by injection autogenous femoral artery blood into the front pool of optic chiasma. Neurologic deficit score were tested with Kaoutzanis M scale. HE dye was used to identify the model. The Cx43 proteins in the basilar arteries were detected by Western blot. Whole cell patch clamp technique was used to record the electrophysiological changes of gap junction channels in basilar arteries. Results The scores of the neurobehavior significantly decreased in the 3 d, 5 d, 7 d and 14 d in operation group(8.33±0.38, 6.67±0.20, 4.83±0.31, 9.33±0.51, respectively) and showed significant difference compared with the control and sham group (P<0.01). There was statistically significance between the different time points(P<0.01). The scores of treatment group were 10.00±0.65, 10.17±0.66, 9.83±0.61, 10.67±0.70 respectively and the difference was statistical significance(P<0.01) compared with the operation group. The expression of the Cx43 protein increased in the 1 d, 3 d, 5 d, 7 d and 14 d after operation which were (0.289±0.01)%, (0.389±0.008)%, (0.51±0.006)%, (0.651±0.019)%, (0.329±0.151)%, respectively and had statistical significance (P<0.01) compared with the control and sham group. There were statistical significance among the different time points(P<0.01). The expression were (0.225±0.007)%, (0.228±0.01)%, (0.251±0.02)%, (0.303±0.008)%, (0.267±0.008)% in the 1st, 3rd, 5th, 7th, and14th day after treatment and had statistical significance compared with the control and sham group(P<0.01). The conductivities were (3.07±0.19)nS/m, (4.88±0.34)nS/m, (8.20±0.31)nS/m, (11.94±0.22)nS/m, (4.07±0.22)nS/m, respectively, and had important increment in the 1st, 3rd, 5th, 7th and 14th day after operation compared with the control and sham operation group (P<0.01). There were statistically significance in the different time points(P<0.01). And the data of the treatment group were (1.38±0.16)nS/m, (1.64±0.15)nS/m, (2.26±0.21)nS/m, (2.89±0.85)nS/m, (2.11±0.20)nS/m respectively and had statistical significance compared with the operation group(P<0.01). Conclusions Cx43 proteins play an important role in the pathomechanism of cerebral vasospasm after experimental subarachnoid hemorrhage.Gap junction inhibitor 18β-glycyrrhetinic-acid can relieve cerebral vasospasm after experimental subarachnoid hemorrhage in rats in vivo. Key words: Cerebral vasospasm; Cx43; 18β-glycyrrhetinic-acid; Whole cell patch clamp technique