Name: extraction and dissection of the domesticated pig brain
Uploaded: 2021-04-25T14:00:00
Description: Watch this Scientific Journal Video about Extraction and Dissection of the Domesticated Pig Brain at JoVE.com

The authors would like to acknowledge Jim Knoblauch and Martin-Booth Hodges of the College of Agricultural, Consumer and Environmental Sciences Information Technology and Communication Services for their expertise in shooting, recording, and editing audio and video.

Procedures involving animal subjects have been approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Illinois at Urbana-Champaign
NOTE: Prior to euthanasia, the pig was anesthetized via intramuscular injection with a combination of telazol:ketamine:xylazine (50.0 mg of tiletamine HCl plus 50.0 mg of zolazepam HCl reconstituted with 2.50 mL of ketamine HCl (100 g/L) and 2.50 mL of xylazine (100 g/L) and administered at 0.06 mg/kg BW). Once anesthetized, the pi...

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The techniques described herein were designed for pigs approximately 4 weeks of age. It is critical to perform these steps immediately after the pig has been humanely euthanized to ensure the integrity of brain tissue structure is maintained, especially when considering subsequent biochemical assays. It is helpful to use an atlas or fiber16 dissection guides when first learning the techniques. It is recommended that the experimenter practice several brain extractions and dissections prior to obtai...

The pig has been well documented and accepted as a translatable animal model for research in cardiovascular systems1, gastrointestinal systems2, nutrition3,4, diabetes5, toxicology6, and surgical techniques7. Use of the pig in neuroscience is beginning to increase, as PubMed searches for the keywords &#34;swine brain animal model&#34; result in four-times more results from 1996-2005 than the preceding 10 year period8, and even more results at present. A primary reason that the popularity of the pig model is expanding is due to its similarities in growth, structure, and function of the brain when compared with humans. In comparison to the human brain, the pig brain exhibits similar gyral patterning, vascularization and distribution of gray and white matter9. Moreover, the pig brain has been used in neuroimaging procedures, evoked potential recording, and in establishing neurosurgery techniques8,9. Unlike other animal models, however, the pig and human experience perinatal brain growth spurts, as opposed to pre- or post-natal growth spurts. At birth, the human and pig brain weigh approximately 27 and 25 percent of their adult brain weight, respectively, compared to the rat brain that weighs 12 percent of its adult brain weight and the rhesus monkey brain at 76 percent of adult weight10.
One reason the pig has been only slowly adopted as an animal model for neuroscience is because many researchers are unfamiliar with the animal in this context. Researchers may not be aware of its potential uses in the field or may not know the proper techniques required to use such a model. As use of the pig as a biomedical and preclinical model gains attention and use in neuroscience, it is necessary to establish standardized procedures of tissue removal to ensure accurate comparison of data across studies. Although dissection and surgical techniques involving the pig brain have been published elsewhere11,12,13, there is a need for simple and standardized protocols to collect pig brain tissue, especially for use in biochemical assays. As such, the aim of this video is to provide the knowledge necessary to allow researchers to perform a standardized brain extraction and dissection. This video illustrates one proper technique to remove the pig brain while keeping the cortex and brainstem intact, and subsequently review methods to dissect several key brain regions.

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extraction and dissection of the domesticated pig brain

Use of the pig as a preclinical and translatable animal model has been well-documented and accepted by research fields investigating cardiovascular systems, gastrointestinal systems, and nutrition, and the pig is increasingly being used as a large animal model in neuroscience. Furthermore, the pig is an accepted model to study neurodevelopment as it displays brain growth and development patterns similar to what occurs in humans. As a less common animal model in neuroscience, surgical and dissection procedures on pigs may not be as familiar or well-practiced among researchers. Therefore, a standardized visual protocol detailing consistent extraction and dissection methods may prove valuable for researchers working with the pig. The following video showcases a technique to remove the pig brain while keeping the cortex and brainstem intact and reviews methods to dissect several commonly investigated brain regions including the brainstem, cerebellum, midbrain, hippocampus, striatum, thalamus, and medial prefrontal cortex. The purpose of this video is to provide researchers with the tools and knowledge necessary to consistently perform a brain extraction and dissection on the four-week-old pig.

This section describes examples of results obtained after correct extraction and dissection of a 4-week-old pig brain. Figure 1 outlines the shape of each brain region for use as a guide during dissection. Part of the brainstem may remain in the skull after removal of the cerebellum (Figure 1B). This can be removed while isolating the desired region of the cerebellum. Table 1 displays the average weight (mean &#177; standard error of the mean) f...

Watch this Scientific Journal Video about Extraction and Dissection of the Domesticated Pig Brain at JoVE.com

Extraction and Dissection of the Domesticated Pig Brain

This protocol details the technique for removal of the pig brain in its entirety and dissection of several brain regions commonly studied in neuroscience.

Use of the pig as a preclinical and translatable animal model has been well-documented and accepted by research fields investigating cardiovascular ...

The following video is a demonstration of removal and dissection of the pig brain. It may be helpful to refer to an atlas, or fiber dissection guide before or during the procedure. A large butcher knife is best for decapitation as it will allow for one clean cut between the atlas and axis.Ensure the knife is sharp before starting with a new subject. A meat hook is used to remove the skull. A long slender tool such as a scalpel handle is used to remove the brain from the skull.A vice with screws or protrusions is necessary to secure the head while cutting the skull. Once the animal has been humanely euthanized according to established protocols proceed as follows. Cut just above the nape of the neck, between the shoulders and the top of the head.Secure the pig and move the years out of the way during decapitation. Use a scalpel to make incisions to separate the skin from the skull. Make an initial cut on the middle of the skull that continues to the posterior of the head.The second transverse cut should be on the posterior of the head. The third cut also transverse will start at the posterior of this snout, and inline with the eyes to ensure easy access to the skull. Use a bone saw to make to anterior to posterior cuts lateral to the midline.Start by lightly marking the area for the cut with the saw, and then begin sawing until you meet less resistance from the skull. Slightly bevel the saw toward the midline while cutting as this will ensure that you are cutting the thinnest part of the skull. If the cut is too close to the ear it will be difficult to remove the skull.But if the cut is too close to the midline the opening will be too small to remove the brain. Repeat this process on the perpendicular sides to create a rectangular window. Ensure that each corner of the window is completely cut, so that part of the skull can be removed to reveal the brain beneath.Next, use a meat hook or curved instrument to pry the rectangular skull section out of position. Start by placing the hook into one of the corners, and applying pressure to pop the skullcap off. In some cases, the meninges will remain on the brain.And if this occurs carefully use forceps and blunt scissors, or alternatively a scalpel to remove the meninges without cutting the brain. For reference the brain should look as follows before and after the meningeal layers have been removed. Cut through the muscle and fat on the posterior of the head to prepare for exposure of the cerebellum.To expose the cerebellum make two transverse cuts along the posterior of the skull. When making these cuts take care to not cut into the exposed brain. Once the cuts have been made place one hand on the snout, and one on the skull, and apply backwards pressure to pull the posterior portion of the skull away from the rest of the head.As highlighted here, the cerebellum is tucked behind the remaining meningeal layers. Use the end of a blunt instrument like a scalpel handle to carefully separate the brain from the skull, taking care to avoid damaging the brain in the process. Slightly invert the head to help coax the brain out of the skull, and use a gentle scooping motion to sever the cranial nerves and remove the brain.This process requires patience and practice to eliminate all remaining connections between the brain and cranial cavity. Inverting the pig's head can be helpful during this process. Continue using sweeping motions with the blunt instrument to free the brain.As highlighted here, the cerebellum and brainstem may be difficult to remove as they are tucked into the skull cavity. Take care when removing the cerebellum and medulla, or brainstem. The brain should fall out on its own when it is completely detached from the skull.The skull cavity should look as shown after removal of the brain. In preparation for brain region dissection ensure pre-labeled containers are organized, and in close proximity. Example preservation methods include snap freezing samples in liquid nitrogen, or submerging them in a preservative solution.Once extracted from the cranial cavity the whole brain should look as follows. To remove the medulla or brainstem, make a coronal cut caudal to the cerebellum. To remove the cerebellum, make a coronal cut posterior to the cortex.To separate the hemispheres make a midsagittal cut along the longitudinal fissure using a continuous motion to prevent damage. For the purposes of this video we will only show dissections from the right hemisphere. To remove the midbrain look for the superior, and inferior colliculi which are two bumps on the posterior portion of the brain.Remove the desired amount of brain tissue just ventral to these regions. To remove the hippocampus position the scalpel handle on the posterior of the corpus callosum, and gently roll the hippocampus out. The entire hippocampus horn will be bean shaped.The hippocampus should easily roll out when scooping your finger in a j-motion, starting from the posterior corpus callosum. To remove the striatum or caudate nucleus clear away the anterior portion of the corpus callosum. The caudate nucleus is the striated or striped region that's colored gray and white and located just below the corpus callosum.With the scalpel handle angled remove this region which predominantly includes the caudate nucleus. After removing this tissue you should be able to see a striated pattern where the brain region had been located. To remove the medial prefrontal cortex dissected tissue from the frontal gyrus to the corpus callosum taking the most medial portion of that section.The right cortex should remain after removal of the medial prefrontal cortex. To remove the thalamus, remove the bulb like structure at the center of the midsagittal surface. The thalamus has an obvious spherical shape, and it will look slightly darker than the surrounding tissue.Upon completion of the dissection tissue samples should be preserved properly based on specific experimental outcomes. Shown here are the dissected brain regions, including the relative size and shape expected when working with young pigs. Upon mastering these techniques, the entire brain extraction, and dissection procedure will take less than 15 minutes per subject, and produce consistent results.

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