Standardization of deer brain dissection and characterization of the deer hippocampus and its subregions

Abstract

An ongoing research project studies the welfare of wild deer populations. Previous studies declared that the adaptive capacity of an animal plays an important role in the wellbeing of animals. A stress response has evolved as such an adaptive capacity. Stress causes activation of the HPA axis, which ends in a negative feedback loop coordinated by glucocorticoid receptors (GR and MR) in the hippocampus of the brain. Animals that experience chronic stress show an imbalance of GR/MR with no or hampered negative feedback as a result. In our research group, we aim to assess chronic stress in wild deer using GR and MR as output parameters. The limited knowledge about deer brain and especially the hippocampus is an important hurdle to overcome in improving the reliability of this research. Related to this, some practical problems regarding dissection of deer brain need to be resolved. This intern research project focussed on these problems and claimed the following goals: (1) to standardize the dissection methods of deer brain by developing a dissecting mold, (2) develop a deer brain atlas by Nissl staining the slides with particular focus on the hippocampus and (3) to dissociate the subregions CA1, CA3 and the dentate gyrus of the hippocampus using an immunohistochemistry procedure with antibodies against PKC-beta, PKC-delta and NPY1, respectively. A dissection mold was developed for fallow deer. This mold will allow standardized dissection of deer brain in coronal slices and consistent collection of hippocampus tissue in the exact same anatomical orientation. A detailed fallow deer hippocampus atlas was made to visualize the 3D orientation of the hippocampus in deer brain. With immunohistochemistry we identified NPY1 as a marker for the dentate gyrus region in the hippocampus, but markers for the CA1 and CA3 subregions are yet to be identified. Taken together, the tools generated in this project allow for reliable and consistent analysis of GR and MR in fallow deer hippocampus.