Additional file 3. Montage image showing a large section of porcine spleen stained for NPY. NPY + nerve fibers were found in all regions of pig spleen, with red pulp being the most densely innervated. White pulp (wp), red pulp (rp), and trabeculae (t) are labeled. Montage was created by stitching multiple 10X images using an Olympus BX41 microscope equipped with an Olympus DP74 digital camera and cellSens Dimension software.