Brain fixation for analysis of brain lipid-mediators of signal transduction and brain eicosanoids requires head-focused microwave irradiation: an historical perspective.

ABSTRACT

To microwave or not to microwave, that is the question that has confounded the neurochemist as the quest for reducing changes in neurochemicals associated with post-mortem delay has evolved over the years. Rapid changes in brain constituents during the post-mortem delay have been recognized for years as a problem. What is real and what is artifact? What are true basal levels of molecules found in the brain? In the 1920s, neurochemists recognized this issue and determined freezing of the brain was most advantageous for halting rapid breakdown of some molecules and rapid formation of others. By the early 1970s, a number of laboratories noted that freezing the brain in situ or upon removing it from the cranial vault was not sufficient to reduce alterations in brain chemistry. Groups began experimenting with two different techniques to attack this problem, freeze-blowing and head-focused microwave irradiation. My laboratory and others have found that the utilization of head-focused microwave irradiation to halt enzymic alterations in lipids is an essential tool to limit alterations post-mortem. Recently, we and others have demonstrated that this technique is essential in reliably assessing brain eicosanoid levels, without such fixation true basal levels of eicosanoids are impossible to determine and the high concentrations seen in some paradigms may be merely an artifact produced during handling of the brain. Thus, for eicosanoid analysis and other applications in measuring brain lipid levels, head-focused microwave irradiation is an essential tool for the lipid neurochemist.