Adenosine Receptor A2a Agonists On Spontaneous Intracerebral Hemorrhage In Rat Brain Protection

[ENGLISH ABSTRACT ]Intracerebral hemorrhage (ICH) refers to spontaneous non-traumatic bleeding into brain parenchyma without underlying causes of vascular abnormalities (such as arteriovenous malformations and aneurysms). It accounts for 10%-20% of all subtypes of strokes but with the highest disability and mortality. Neither surgery nor medical treatment has been proven efficacy and superior to the other so far in the views of evidence-based medicine. Therefore, the study of neuroprotection from ICH continues to be an emergent challenge.Acute inflammatory response to spontaneous intracerebral hemorrhage tends to be significantly greater than ischemic stroke of similar size. So inflammation becomes the potential target of neuroprotection. Recently, the subtype A2a of Adenosine receptors (ARs) has been shown to be a critical part of the physiological negative feedback mechanism for limitation and termination of inflammatory response. Synthetic A2a selective AR agonists as novel anti-inflammatory agents are in pre-clinical trials for treatment of allergen-induced inflammation, ischemia-reperfusion injury, sepsis, and autoimmune disease. Will it also work in the setting of ICH, which remain unsolved. We are supposed to observe the efficacy of intracerebral administration of the synthetic A2a selective AR agonist into rats following intracerebral hemorrhage and further explore underlying mechanisms of neuroprotection.Part OneBehavioral Tests OfSpontaneous Intracerebral hemorrhage In RatsObjective: To develop a rat model of spontaneous intracerebral hemorrhage(ICH) and choose a battery of behaviorial tests to evaluate the neurological outcome of the ICH rats. Methods: The design of experimental protocol employed prospective case-control randomized study. Forelimb placing and corner turn test were chosen as the behavioral tests. The rats were tested from day 1 to day 7 after stereotaxic infusion 100ul autologous arterial blood into right basal ganglion or saline instead as contrast. Pathologic features of both intracerebral hematomas and secondary brain injuries were assessed at day 1 following the above procedures. Results: The battery of behaviorial tests indicated that there were marked neurological deficits at day 1 after ICH that persisted to day 3 and relieved incompletely at day 7, which demonstratedasymmetry both in forelimb use and in corner turning. Brain dissections revealed hematomas located in right basal ganglion with regular contour all but one case complicated with ventricular hemorrhage accounted for 10%(l/10). Tissue necrosis> edema and inflammation were identified in the perihematoma region in the hematoxylin-eosin stains of lesion-based sections. Conclusion: Stereotaxic infusion autologous blood into basal ganglion is a straightforward and effective technique to produce a reproducible and comparable ICH model in the rats. The model can provide necessary information about pathophysiological events after intracerebral hemorrhage. Both the behavioral tests allow continuous monitoring and quantization of neurological deficits after rat ICH and make a tool of assessment of therapeutic interventions.Part TwoCGS21680 Reduces Brain Edema and Ameliorates Neurological DeficitsFollowing Acute Intracerebral Hemorrhage in RatsObjective: To test the hypothesis that CGS21680, a highly selective agonist for adenosine receptor A2a , can reduce brain edema and thus ameliorate neurological deficits in the rat model of intracerebral hemorrhage. Methods: Experimental intracerebral hematoma was induced in SD rats as described in Part One. These rats with intracerebral hematoma were randomly assigned to receive either CGS21680, ZM241385 or nothing in Group CGS, Group ZM and Group ICH respectively. Meanwhile, 0.05% DMOS (dissolved in saline) was administrated intrastriately to control rats named as Group Sham. Brain water content was measured and neurological outcome was assessed by the battery of behavioral tests described in Part One at 1 and 3 days after induction of intracerebral hematoma. Assay of myeloperoxidase (MPO) activity combined with morphological identification was to quantify and compare neutrophil infiltration in the perihematomal region among these groups at 1 day. Results: The brain water content of Group CGS decreased in the lesioned hemisphere but that of Group ZM which increased did not differ from that of Group ICH significantly at 1 and 3 days. The neurological behavioral deficits in Group CGS ameliorated but these in Group ZM exacerbated the same as did in Group ICH at 1 and 3 days. Neutrophil infiltration was intenser in Group ZM and sparser in...