Microglial P2X7 receptor in the hypothalamic paraventricular nuclei contributes to sympathoexcitatory responses in acute myocardial infarction rat

Several pieces of evidence indicate that the microglial P2X(7) receptor (P2X(7)R) regulate cardiovascular activities. We explored the possible roles of microglial P2X(7)R in the PVN mediated sympathoexcitatory responses in acute myocardial infarction (AMI) rat. Sprague-Dawley rats underwent coronary artery ligation to induce AMI. The rats received intraperitoneal administration of the P2X(7)R antagonist Brilliant Blue-G (BBG, 25 or 50 mg kg(-1), once a day for 5 days) prior to myocardial ischemia. Other rats received bilateral microinjection of P2X(7)R-siRNA (0.015 or 0.03 nmol 0.1 mu l per side, once a day for 2 days) targeting P2X(7)R mRNA into the PVN prior to myocardial ischemia. First, we examined the ATP levels and protein expression P2X(7)R in the PVN in different ischemia time groups, and we found that the change of P2X(7)R was positive correlated with the ATP levels in a time-dependent manner. The double-immunofluorescence evidence showed that P2X(7)R was mainly co-localizated with the microglial marker lba-1 in the PVN. Second, gene knockdown of P2X(7)R with P2X(7)-siRNA or inhibition of P2X(7)R with BBG reduce the mRNA and protein expression of IL-1 beta and TNF-alpha in the PVN of AMI rat. Third, microinjected P2X(7)-siRNA also suppressed the up-regulation of P2X(7)R, oxytocin and vasopressin in the PVN of AMI rats. Fourth, P2X(7)-siRNA and BBG also attenuated the renal sympathetic nerve activity (RSNA) in the AMI rats. Our results indicate that microglial P2X(7)R activation in PVN mediating the production of proinflammatory cytokines that activate oxytocinergic and vasopressinergic neuron, which augmented the RSNA in the AMI rat. (C) 2014 Elsevier Ireland Ltd. All rights reserved.