The MacBrain Resource Center (MBRC) rhesus macaque postnatal brain histology datasets: Enabling new discoveries through NHP tissue and digital data Repositories.

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 (