Isoflurane and Ketamine/Xylazine Anesthesia do not Influence the Neuroprotective Effects of Simvastatin in a Model of Permanent Cerebral Ischemic Injury in C57BL/6J Mice

Abstract

Laboratory mice with Middle Cerebral Artery Occlusion (MCAO) represent the main animal models for ischemic stroke research. Appropriate anesthetic protocols are essential, as anesthetic agents might affect the central nervous system (CNS) and therefore interfere with the outcome of pre-clinical ischemic stroke studies. In the present study we sought to investigate whether isoflurane, a widely used inhalational anesthetic, has any effect on MCAO mice pretreated with simvastatin, a well-known neuroprotective compound, compared with the administration of injectable ketamine/xylazine combination. Forty adult C57Bl/6J mice randomly allocated into four groups underwent ischemic injury by permanent coagulation of the Middle Cerebral Artery (MCA): Group A (n=11) animals were anesthetized with ketamine/xylazine, Group B (n=9) with isoflurane, Group C (n=9) with ketamine/xylazine after pretreatment with simvastatin 2h before permanent Middle Cerebral Artery Occlusion (pMCAO) and Group D (n=11) with isoflurane after similar pretreatment with simvastatin. The potential neuroprotective effect of the anesthetics was evaluated in terms of brain infarct volumes and neuron death. No significant differences, both quantitatively and qualitatively, were detected in brain lesions measured up to 7 days after pMCAO when comparing isoflurane inhalational anesthesia to ketamine/xylazine injectable anesthesia. Group C mice (simvastatin-treated ketamine/xylazine) had a significantly reduced brain infarct volume compared to Group A mice (non-simvastatin ketamine/xylazine) (P<.0005). Similarly Group D mice (simvastatin-treated isoflurane) had a significantly reduced brain infarct volume compared to Group B mice (non-simvastatin isoflurane) (P<.0005). No difference between morphology and number of apoptotic neurons was detected due to the two different anesthetic regimens. These results demonstrated the safe use of the established anesthetic agent isoflurane in mice where simvastatin is investigated as a neuroprotective compound.