The Whole-body Fixation Method of Rats using Modified-Farmer’s Fixative for Gross Anatomy

Abstract

Anatomy and physiology of human body are essential and fundamental subjects for medical or nutritional sciences. In medical and nutrition training organizations, dissection of small animals such as rats and mice are often carried out for the purpose of learning the structure and function of the human body. This is a very useful or effective methods to understand the three-dimensional (3D) structures of anatomy. However, in most cases, the anatomical practices for students will not gain the sufficient educational effects comparable to the cost of sacrificing animals due to the shortage of training time. We have previously reported an animal fixation method that can be carried out conveniently, safely, and repeatedly in rats by using of Farmer’s fixative. This liquid consists of mixture with acetic acid and ethanol (acetic acid:ethanol; 1:3, v:v). Although this method made it possible to dissect, anatomize, and observe various tissues and organs, there are several weaknesses such as insufficiency of fixation in deep organs. In order to solve or alleviate these defects, the authors changed the fixing method and the composition of the fixing solution and evaluated the qualities of specimens fixed with our present method. In this experiments, it was found that performing immersion fixation in addition to perfusion fixation and using a concentration of acetic acid: ethanol at 1:7 as the perfusion fixative are most appropriate condition for anatomical practices. Through these improvements, we were able to make specimens of rat more suitable for dissection training and detailed observations. Furthermore, since this method can be used repeatedly without scarifying new experimental living animals, it is possible to realize “Reduction” in 3R. In this paper, we mainly discuss on improvements and qualities by comparing our previous method with present procedure.