Technical guide for nervous system sampling of the cynomolgus monkey for general toxicity studies

For general toxicity studies, a technique was designed to consistently sample the most important neuroanatomic regions of the brain, spinal cord, and peripheral nerve of cynomolgus monkeys using a limited number of blocks and slides. Using the most rostral portion of the pons as a landmark, the entire fixed brain was cut dorsoventrally into cross-sectional slabs 4 mm in thickness. For microscopic evaluation, six blocks of the brain at the levels of the frontal pole, anterior commissure, rostral thalamus, caudal thalamus, middle cerebellum with brainstem, and occipital lobe were trimmed to fit in standard tissue cassettes. Cross- and oblique sections of the spinal cord including the dorsal root ganglion and dorsal and ventral nerve roots were obtained at the levels of C1-C4, T10-T12, and L1-L4. Cross- and longitudinal sections of the sciatic nerve were also obtained. This technique offers a consistent and reliable method to routinely sample most of the important regions of the central and peripheral nervous system of monkeys using ten blocks. This method is readily adaptable to other species of nonhuman primates, dogs, and minipigs and can be quickly learned by the technicians performing the trimming procedures.