The MacBrain Resource Center (MBRC) rhesus macaque postnatal brain histology datasets: Enabling new discoveries...

In our companion paper, in this issue, we describe our efforts to provide embryonic rhesus macaque (Macaca mulatta) brain histology for the study of brain development, with emphasis on cortical development. Here we continue our description of efforts to provide postnatal rhesus macaque brain histology relevant for the study of cellular circuits which continue to mature and change well into postnatal life, in males and females, and which naturally deteriorate in the elderly. The mission of the MacBrain Resource Center (MBRC) in the Department of Neuroscience at Yale University School of Medicine is to provide a cost-effective means for researchers to conduct de novo studies on this non-human primate (NHP) brain animal model using materials already in existence and therefore without exorbitant costs and without having to sacrifice additional animals (https://medicine.yale.edu/neuroscience/macbrain/mission/). Here we report on how this mission is being accomplished. Because MBRC materials have been and continue to be gathered from unrelated studies over many years, most methods have already been published. The MBRC divides different types of materials into separate Collections. The present description of histo- and immunohistochemical processes is limited to current work that provides materials to populate Collection 6 and is accurate as of May 2026. Collections in the MBRC are dynamic. Of the 8 current MBRC datasets, here we emphasize Collections 5, 6, and 7 and illustrate through examples how different materials are currently being used to conduct research both in cortical and subcortical structures. Many of the electron microscopy (EM) blocks in Collection 5 sampling the brain at numerous regions come from the >100 cases of titrated thymidine (³H-TdR) injections in Collection 1 in addition to cases in Collections 2 and 3. Altogether, at present there are ~1000 inventoried EM blocks collected from postnatal cases. Collection 6 currently contains >30,000 digital images illustrating 35 different cellular and fiber markers in 32 brains of both sexes ranging from P0 to 32 years of age. Materials in Collections 6 and 7 keep growing as we constantly process and add NHP brains to them. Based on the molecular, genetic, and anatomical similarities between this animal model and human, we underline the importance of archiving and (re-)using rhesus macaque brains to foster neuroscience research. As far as we know the NHP brain materials in the MBRC Collections constitute the largest datasets of their kind in the world.