Abstract WP220: Platelet Inhibition Prevents Delayed Cerebral Ischemia After Subarachnoid Hemorrhage In Mice

Subarachnoid hemorrhage (SAH) induces delayed cerebral ischemia (DCI) in about 30% of patients which is characterized by functional decline. As microthrombi is a cause of DCI, platelets may be a therapeutic target for preventing microthrombi formation and development of DCI. Clinical trials of anti-platelets have been inconclusive for their effect on outcome. However, clinical trials used different anti-platelets. Since platelets have numerous receptors which can each prevent thrombosis, there is no clear choice to target for SAH. Here, we utilize 6 platelet antagonists to identify if any receptor is a therapeutic target for DCI after SAH. Our hypothesis is that P2Y receptor inhibition will prevent microthrombi and reduce DCI after SAH. Male and female mice were randomly assigned into sham, SAH+vehicle, SAH+P2Y antagonism, SAH+PAR4 antagonism, SAH+PAF antagonism, SAH+TPβ-R antagonism, and SAH+GPIIb/IIIa antagonism. Mice were euthanized 2 (n=10/group) or 7 days (n=15/group) post-SAH. All outcomes were performed and data was analyzed by a blinded investigator. Behavior was assessed daily. Brain microthrombi were counted. Both male and female SAH mice treated with inhibitors of PAF and TPβ-R had significantly better day 1 function than vehicle-treated mice. Significantly better function on day 1 was also observed in only male mice treated the P2Y antagonists or GPIIb/IIIa antagonist. Neither sex had improved behavior for the PAR-4 inhibitor. Mice exhibiting better function had fewer brain microthrombi with the exception of the GPIIb/IIIa antagonist which reduced microthrombi in female mice but did not correspond with improved behavior. This suggests there may be another deleterious mechanism which is more prevalent/detrimental in females that is not prevented by GPIIb/IIIa inhibition, such as platelet degranulation. However, this needs to be further investigated. Additionally, inhibition of TPβ-R reduced the incidence of DCI compared to vehicle-treated mice. In conclusion, an anti-platelet drug for SAH needs to be chosen carefully as not all antagonists have a beneficial effect after SAH; of vital importance is that anti-platelet drugs may not have similar beneficial effects in both sexes.