Study On The Effect And Mechanism Of Hyperbaric Oxygen On Delayed Cerebral Vasospasm Secondary To Subarachnoid Hemorrhage In Rats

Objective: To investigate the effect and mechanism of hyperbaricoxygen(HBO) on the levels of endothelin-1(ET-1) and nitric oxide (NO) inrats with delayed cerebral vasospasm (DCVS) secondary to subarachnoidhemorrhage (SAH).Methods:96healthy male adult Sprague-Dawley rats were randomlyassigned to control group (n=6), sham operation group (n=30), simple SAHgroup (n=30) and SAH+HBO group (n=30). Rats in sham operation group,simple SAH group and SAH+HBO group were randomly divided into5subgroup according5different time points (1d,3d,5d,7d,12d) respectively.Rats in the control group were fed for12days without any intervention andwere executed on the last day. The SAH model in the simple SAH group andin the SAH+HBO group were made by double injection of autologous bloodinto cisterna magna, while in the sham operation group, only normal salinewas injected. After the SAH model had been made successfully,rats in thesubgroups of SAH+HBO group were treated with hyperbaric oxygen therapyfor1day,3days,5days,7days,12days, respectively. Samples of arterialblood, cerebrospinal fluid and right middle cerebral artery in each group werecollected at the preconcerted time points. Endothelin-1(ET-1) level in theplasma and CSF samples were assessed using enzyme-linked immuno sorbentassay (ELISA); Nitrite and nitrate concentration was used as a marker ofnitric oxide production in plasma and CSF samples and was determined by nitrate reductase method. Inner diameter and thickness of the middle cerebralartery (MCA) were measured by microscopic image analysis system. Thedegree of cerebral vasospasm was evaluated by the ratio of the thickness ofthe middle cerebral artery vs. its inner diameter. Pearson correlation analysisbetween the degree of cerebral vasospasm and the levels of ET-1and NO bothin plasma and CSF was estimated. The therapeutic effect of HBO on DCVSwas observed, and the relationship between the therapeutic effect of HBO andthe levels of NO and ET-1both in CSF and plasma samples were furtheranalyzed respectively.Results:1. After operation, the inner diameter of MCA was contracted both in theSAH group and the SAH+HBO group, but the wall thickness of MCA wasincreased. In the SAH+HBO group,the inner diameter of MCA was longerthan that in the simple SAH group on day3,5,7, after operation, but shorterthan that in the sham operation group and control group respectively. Thethickness of MCA in the SAH+HBO group on day3,5,7after operation wasthinner than that in the simple SAH group, but thicker than that in shamoperation group and control group, respectively (P <0.05). Compared withsham operation group or control group,no statistical significances were foundin the inner diameter and the wall thickness of MCA in the SAH+HBO groupboth on day1and day12after operation (P>0.05).2. In the simple SAH group, the NO levels both in plasma andcerebrospinal fluid (CSF) on day1,3,5,7after operation were lower thanthose in the sham operation group and control group (P<0.05), the ET-1levels in CSF on day1,3,5after operation were higher than those in the shamoperation group and control group (P<0.05), the ET-1levels in plasma on day 3,5,7after operation were higher than those in the sham operation group andcontrol group (P<0.05).3. In the SAH+HBO group,the NO levels in plasma and CSF on day1,3,5,7after operation were higher than those in the simple SAH group, butlower than those in the sham operation group and control group, respectively(P<0.05); the ET-1levels in plasma on day3,5after operation were lowerthan those in the simple SAH group, but higher than those in the shamoperation group or control group (P<0.05), the ET-1levels in CSF on day1,3,5,7after operation were lower than those in the simple SAH group (P<0.05),but higher than those in the sham operation group or control group on day5(P<0.05).4. In the SAH group, there was a better positive correlation between theET-1levels and the degree of cerebral vasospasm for both in the plasma (R~2=0.843, P<0.01) and in the CSF (R~2=0.816, P<0.01), while a negativecorrelation existed between the NO levels and the degree of cerebralvasospasm for both in the plasma (R~2=0.561, P<0.01) and in the CSF(R~2=0.347, P<0.05)Conclusions:1. The levels of nitric oxide either in CSF or in plasma was decreasedand had a negatively correlation with the degree of cerebral vasospasm (CVS)secondary to subarachnoid hemorrhage in rats.2. The levels of endothelin-1both in CSF and plasma were increased andhad a positively correlation with the degree of CVS secondary tosubarachnoid hemorrhage in rats3. Hyperbaric oxygen (HBO) therapy can effectively reduce the degreeof delayed cerebral vasospasm secondary to subarachnoid hemorrhage may be through regulating the levels of nitric oxide and endothelin-1in plasma and inCSF in rats.