Transcardial perfusion is not required to accurately measure cytokines within the brain

Background: Cytokines are key signaling molecules within the immune system that regulate a host's response to pathogens and neuronal damage. Aberrant cytokine signaling has been implicated in many neurological diseases. Therefore, accurately measuring cytokine concentrations within the brain is crucial. New method: This study demonstrates that removing blood within brain vasculature via saline perfusion does not alter brain parenchymal cytokine protein concentrations or mRNA expression. Results: Hippocampal protein and mRNA data demonstrate that brain parenchymal cytokine concentrations do not significantly differ based on the method of euthanasia (i.e., perfusion or no perfusion). These results are consistent within naive and immune challenged mice. Comparison with existing method: Due to the potential of cytokine contamination from circulating blood, it is believed that transcardial perfusion is required for accurate measurement of cytokine concentrations and gene expression within the brain. However, our data indicate that cytokine concentrations are unaffected by not perfusing mice with saline prior to tissue collection. Conclusions: Brain cytokine concentrations are unaffected by perfusing with saline prior to tissue collection; this holds true regardless of immune status (homeostatic or immune challenged), suggesting that this time-consuming step may be unnecessary.