Perfusion Fixation of Research Animals

Abstract

Perfusion, washing out blood and using the open vascular channel to infuse fixative, is the standard first step of preparing animal tissues for later examination under a microscope. The rapid and homogeneous fixation resulting provides an advantage over immersion fixation that is usually used for biopsy and clinical tissue samples (Cammermeyer, 1960, Garman, 1990). A disadvantage is that brain tissue, and probably other soft tissues, prepared by perfusion has no retained extracellular space post perfusion, although living brain has about 20% extracellular space (discussed in Cragg, 1980). Perfused brain is also about 20% shrunk in whole organ volume from living brain size. The shrinkage is uneven, and distorts the relationships of structures. It is possible to avoid the organ shrinkage and distortion that follows a traditional perfusion, with little additional effort. This is a discussion of how to optimize your perfusion results, why the shrinkage occurs, and how it can be avoided.