Anatomy and connectivity of the Göttingen minipig subgenual cortex (Brodmann area 25 homologue)

Abstract

AbstractBackgroundThe subgenual gyrus is a promising target for deep brain stimulation (DBS) against depression. However, to optimize this treatment modality, we need translational animal models.AimTo describe the anatomy and connectivity of the Göttingen minipig subgenual area (sgC).Materials and methodsThe frontal pole of 5 minipigs was cryosectioned into 40 µm coronal and horizontal sections and stained with Nissl and NeuN-immunohistochemistry to visualize cytoarchitecture and cortical lamination. Eight animals were unilaterally stereotaxically injected in the sgC with anterograde (BDA) and retrograde (FluroGold) tracers to reveal the sgC connectivity.ResultsIn homology with human nomenclature (Brodmann 1909), it can be subdivided into three distinct areas named area 25 (BA25), area 33 (BA33), and indusium griseum (IG). BA25 is a narrow agranular cortex, approximately 1 mm thick. It has a poor laminar differentiation in the deeper layers due to a similar appearance of layer III and V neurons. Perpendicular to the surface cell, poor columns of white matter stretch deep into layers II and III, thereby segregating small groups of closely arranged neurons in the superficial layers. BA33 is less differentiated than BA25. Accordingly, the cortex is narrower and displays a complete lack of laminar differentiation due to diffusely arranged small, lightly stained neurons. It abuts the indusium griseum, which is a neuron-dense band of heavily stained small neurons separating BA33 directly from the corpus callosum and the posteriorly located septum.ConclusionThe minipig sgC displays a cytoarchitectonic pattern and connectivity like the human and may be well suited for further translational studies on BA25-DBS against depression.