Dysregulation Of Glucocorticoid And Its Receptor In Developing Rats After Intracranial Hemorrhage And Follow-up Effect On Neurogenesis

Objective: To explore the impact of neonatal intracranial hemorrhage onhypothalamus-pituitary-adrenocortical axis (HPA axis) and the clinical application ofexogenous glucocorticoids (GC) on this disease by making the neonatal intracranialhemorrhage rat model and observing the pathologic change around the hematoma,detecting the cerebral homogenate corticosterone level, glucocorticoid receptor (GR)expression in hippocampal CA1area and neural cells proliferation in subventricularzone (SVZ).Methods:(1) The intracrainal autologous blood injection model of ICH wasemployed. Ten-day-old Sprague Dawley rat pups of both sexes were randomized intoeleven groups: A: group DEX: ICH model with dexamethasone intraperitonealinjection; B: group RU486: ICH model with RU486intraperitoneal injection; C:control group: normal control with saline intraperitoneal injection; D: sham operatedgroup: sham operation with saline intraperitoneal injection; E: ICH group: ICH modelwith saline intraperitoneal injection, and the subgroups of CON, SHAM and ICH of12h,24h and72h (F～J).(2) Analysis of neurological deficit score: Pretests weredone to exclude abnormal rats. Only rats with a total NDS of0were included andsubjected to ICH. A combination score from a battery of behavioral tests (Posturalflexing test, Circling or sidewalk and Forelimb placing) was used as a comprehensivemeasure of the neurological functional deficits (NDS). The NDS was measured at72-hour after ICH.(3) The levels of cerebral homogenate corticosterone of rats weretested by the emission immunology method.(4) The pathologic change around thehematoma, the expression of GR in hippocampus CA1and the proliferation of SVZcells were examined using Nissl staining, immunofluorescence and BrdU labelseparately.Result:(1) Nissl stain: Under the microscope by the Nissl staining, in group ICH,the neurons around the hematoma present irregularly shaped, karyopyknosis andkaryorrhexis, while in group SHAM and CON the neurons were all well-arranged with more nissl bodies. After intervention by dexamethasone, though still had someswelling, more neurons survived. And nothing change observed in group RU486.(2)NDS:72-hour after the operation, rats in the ICH group showed significant increase inthe total NDS, while group CON and SHAM stayed normal. And the postural flexingtest, circling or sidewalk and forelimb placing deficit in rats treated withdexamethasone were54.55%,69.33%, and54.84%of saline control respectively.Overall there was a significant reduction in the total NDS by57.89%, as comparedwith group CON(P＜0.0001). And group RU486showed no difference with groupCON.(3) Cerebral homogenate corticosterone level: After ICH, the corticosteronelevel in cerebral homogenate climbed up to a peak in about12h, and slowly wentdown. By the end of72h, the corticosterone level was still higher than normal rats atthe same age (P＜0.0001). Dexamethasone helped to speed this process, rats ingroup DEX whose corticosterone level in the brain declined to normal level, whileRU486counteracted the result.(4) Immunofluorescence of the GR: The meanintegrated optical density (IOD) of GR in hippocampal CA1of rats in the ICH groupwere much more smaller than those in group CON (P＜0.0001). But the mean IODof GR showed no difference among group DEX, RU486and ICH(P＞0.05).(5)BrdU label: At the age of13days, namely72-hour after ICH, rats in group ICHrepresent a more dynamic proliferation in the SVZ with more BrdU+cells than groupCON at the same age (P＜0.001), while dexamethasone didn’t change the result.Conclusions:(1) ICH in neonatal rat disturbs the modulation of HPA axis, withan increase in the corticosterone level and less GR expression.(2) Early application ofdexamethasone helps to correct the dysfunction of HPA axis, normalize thecorticosterone level and finally protect the neurons from further injury.(3)Dexamethasone shows no impacts on the expression of GR and the proliferation ofcells of SVZ.