Direct brain excision: An easier method to harvest the pig's brain

The use of pigs in experimental brain research was advocated more than 30 years ago [9]. However, many factors favour the use of rodents in research including the ease of housing and handling of small laboratory rodents, low cost of both procurement and housing, easy access from veterinary sources and relatively low cost compared to other large mammals. Due to these factors rodents are often the preferred population in pre-clinical research but larger animals, specifically pigs, play an important role in research, particularly in translational work [8]. Many of the prerequisites for conducting neuroscience research are fulfilled for pigs, including the need for standardized laboratory breeds, and an advanced knowledge of the general anatomy and physiology, housing, handling and experimental procedures [8]. However, interbreed differences in neuroanatomy and behavioral reactivity are not fully established for different breeds of pigs [8]. Therefore, it is imperative that well-defined or standardized pig breeds should be employed to ensure increased reproducibility and comparability of research. The recent advent of imaging technology for studying brain function and structure in vivo has benefited from the relatively large size of the pig brain. The use of pigs within neuroscience has increased in the past decade to an extent that far exceeds that of other farm large animals, such as sheep [8]. However, basic knowledge about the anatomy, physiology and development of the pig brain is still being collected. A considerable amount has been learned about pig brain anatomy and neurochemistry, but little is known about cortical function [11]. The gyrencephalic pig brain is more similar to the human brain in anatomy, growth and development than are the brains of common small laboratory animals [6,11]. The large size of the pig brain permits the detailed identification of cortical and subcortical structures [11]. Furthermore, the pig is an increasingly popular laboratory animal for transgenic manipulations of neural genes. Wider use of pigs in research could facilitate extrapolation of preclinical findings to humans, especially in research important areas wherein obvious dissimilarities in brain structure and function render rodents less comparable to humans [4]. Thus, developing an easier and faster method to harvest the pig's brain can be beneficial for a full range of neuroscience experiments, as an alternative to research exclusively in rodents and non-human primates. Included below is a pig brain harvesting methodology derived from our labs dual neurosurgical and preclinical pig lab experience. The harvesting technique was applied after the end of experiment in human-size pigs (40–60 kg) after the animal care approval. The technique consists of direct excision without decapitation, which it is faster and easier than previous craniotomies methods using longitudinal and coronal craniotomy. Steps: Mark “T-shape” incision line the pig's skull using anatomical references points: the pig's ears and eyes. Approximately, the length should be around 10 cm and the wide 8 cm. The lines are draw using the midline and the ears as reference points. After the skin incision, using a scalp, remove the periosteal membrane to the skull. The coronal suture and the temporal muscle should be exposed. Draw a hexagon picture in the pig's skull using as reference points: superior orbital bones, glabellum, temporal-parietal skull bones division and parietal-occipital line, as demonstrated in the picture behind. Carefully, with handheld circular saw, cut the bone's skull in the hexagonal lines, controlling the force applied in order to prevent brain tissue damage. (Fig. 1).