Nervous System Sampling for General Toxicity and Neurotoxicity Studies in Rabbits

Although manuscripts for multiple species recommending nervous system sampling for histopathology evaluation in safety assessment have been published in the past 15 years, none have addressed the laboratory rabbit. Here, we describe 2 trimming schemes for evaluating the rabbit brain in nonclinical toxicity studies. In both schemes, the intact brain is cut in the coronal plane to permit bilateral assessment. The first scheme is recommended for general toxicity studies (tier 1) in screening agents where there is no anticipated neurotoxic potential; this 6-section approach is consistent with the Society of Toxicologic Pathology (STP) "best practice" recommendations for brain sampling in nonrodents (Toxicol Pathol 41: 1028-1048, 2013¹). The second trimming scheme is intended for dedicated neurotoxicity studies (tier 2) to characterize known or suspected neurotoxicants where the nervous system is a key target organ. This tier 2 strategy relies on coronal trimming of the whole brain into 3-mm-thick slices and then evaluating 12 sections. Collection of spinal cord, ganglia, and nerve specimens for rabbits during nonclinical studies should follow published STP "best practice" recommendations for sampling the central nervous system¹ and peripheral nervous system (Toxicol Pathol 46: 372-402, 2018²).