MICROVASCULAR CORROSION CASTING OF THE RAT MANDIBULAR JOINT - A TECHNICAL APPROACH

The rat mandibular joint is a ginglymoarthrodial joint deeply hidden u nder the zygomatic process of the squamosal bone. This joint was studi ed by scanning electron microscopy (SEM) of microvascular corrosion ca sts in 47 adult rats. Six additional rats were injected with India ink and thick sections of the joint area were examined by light microscop y. The small size of the joint (2.5 mn x 1.5 mm in occlusion), the exi stence of two slit-like joint compartments, the close proximity of bon es and soft tissues in a mobile structure, and the intimate relationsh ips of the joint with adjacent skeletal muscles made the vascular mapp ing difficult. Five different technical procedures (protocols) were te sted. The most satisfactory approach is, briefly, as follows: each rat was injected simultaneously via both common carotid arteries with 9.5 ml of casting medium (Mercox-CL-2B diluted 4:1 with monomeric methyl methacrylate), and with an additional volume of 0.5 ml of the same med ium after ligation of the external jugular veins used for outflow. Aft er polymerization of the injected resin, the rats were frozen, and the heads were severed and spliced sagittally into two halves. These spec imens were cut in the transversal (coronal) and sagittal planes into s mall blocks. Each block was then cut systematically either in the tran sversal or parasagittal plane running through the joint. Afterwards th ick slices were macerated in warm (45 degrees C) 15% KOH, rinsed, (som e were decalcified in 2% HCl), rinsed again in tap water, frozen in di stilled water, freeze-dried, mounted, dissected, coated and examined u nder the SEM at 5 kV.