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P87 Introduction: Extracellular ATP activates  P2 receptors to increase intracellular Ca2+ , to  contract cerebral arteries, and to induce vasospasm in animals. This  study examined the mRNA expression of P2 receptors in a rat  double hemorrhage model and explored the therapeutic role of  P2 receptor antagonists in a dog double hemorrhage model.Methods: One hundred SD rats were divided into five groups  to undergo double hemorrhage by injecting autologous arterial blood  into cisterna magna on day 0 and 2. Rats were sacrificed on day 3, 5 or  7. In sham group, rats were injected with saline. In control group, no  surgery was conducted. Basilar arteries were harvested for mRNA  isolation and RT-PCR or were fixed for transmission electron microscopy  (TEM). Eighteen dogs were divided into three groups to have double  hemorrhage and sacrificed on day 7. Two groups were treated,  intracisternally, with P2 receptor antagonist suramin  (selective for P2Y and P2X ) or PPADS (selective  for P2X1 ) (30 μM) from day 3–6. Angiograph was performed  before blood injection and before sacrifice. The basilar arteries were  collected for TEM.Results: Mild to moderate vasospasm  (30–40% reduction) was observed on day 3–7 in rats. The mRNA  expression of P2X1 receptor was down-regulated (P&lt;0.05) on  day 3 and recovered on day 5 and 7. P2Y1 and  P2Y2 receptors were up-regulated (P&lt;0.05) on day 5 and  remain elevated on day 7. No changes were observed in the shame group.  Severe vasospasm was observed on day 7 in dogs. P2 receptor  antagonist Suramin but not PPADS significantly reversed (P&lt;0.01,  ANOVA) vasospasm in dogs. Discussion: P2Y1 and  P2Y2 , but not P2X1 , may be involved in cerebral  vasospasm. Up-regulation of P2Y receptor may enable ATP to  produce contraction at low concentrations. Suramin reduced vasospasm  probably by blocking P2Y receptors.

Role of P 2 receptors in Cerebral Vasospasm

Role of P ₂ receptors in Cerebral Vasospasm