Altered Expression of P 2 Receptor mRNAs in the Basilar Artery in a Rat Double Hemorrhage Model

Abstract

Background and Purpose —Extracellular ATP might induce cerebral vasospasm after subarachnoid hemorrhage through P 2 receptor. To investigate the roles of P 2 receptor subtypes in vasospasm, we examined the changes in mRNA expression of P 2 receptor subtypes in basilar arteries from double cisternal blood injection rat models. Methods —One hundred male Sprague-Dawley rats, each weighing 350 to 400 g, were divided into 2 groups of 50. In the first group (n=50), the autologous arterial blood (0.2 to 0.3 mL) was injected into the cisterna magna on days 0 and 2. The rats were killed on day 3, 5, or 7 (n=10 in each group). In the sham group (n=10), the rats were injected with saline (0.3 mL) instead of blood. Ten rats were killed without blood or saline injection and served as control. The basilar arteries from rats in each group were used for reverse transcription and polymerase chain reaction. In another group of 50 rats, the same experiment was conducted, and the basilar arteries were collected for transmission electron microscopic study. Results —In the subarachnoid hemorrhage groups, transmission electron microscopy showed the reduction in vessel perimeter on days 5 and 7 to be approximately 30% to 40%. The P 2X1 mRNA level was significantly decreased on day 3 and recovered on days 5 and 7. The P 2Y1 mRNA level was transiently increased on day 5, and the P 2Y2 mRNA level was elevated from day 5 to day 7 ( P <0.05). Conclusions —The differential expression of the P 2 receptors indicates that P 2X1 subtype might not play an important role in vasospasm. The upregulation of P 2Y1 and P 2Y2 receptors might enable ATP to produce contraction at low levels of concentration.