A rapid approach to ultrastructural evaluation and DNA analysis of the vestibular labyrinth and ganglion in dogs and cats.

The vestibular labyrinth is the organ for sensation of equilibrium. It is part of the inner ear and located in the caudodorsal aspect of the temporal bone which makes it very difficult to access. This study evaluated a preparation technique in cats and dogs for morphological and DNA analysis. The study included 44 temporal bones of 14 cats and 11 dogs collected within 48h after death. Preparation was performed after peri-/endolymphatic injection of Fast-Green-FCF through the fenestra vestibuli to visualize the membranous labyrinth. The vestibular nerve, including its ganglion, and the vestibular labyrinth were exposed by drilling and cracking of the petrous temporal bone along the meatus acusticus internus. The posterior ampulla was collected for histology and transmission electron microscopy whereas the vestibular nerve, the utriculus, sacculus, and the lateral and anterior ampullae were harvested for subsequent DNA analysis. Histology and electron microscopy showed well-preserved cells. A total DNA amount of 4753+/-1502ng in cats and 5865+/-2911ng in dogs was retrieved from the ganglion, and 2390+/-561ng in cats and 2544+/-1277ng in dogs, respectively, from membranous vestibular organs. Polymerase chain reaction of a 229 base pair product of the Gapdh-gene proved for presence of amplifiable DNA. Taken together, mechanical bone removal after Fast-Green-FCF injection allows for reliable gross, microscopic and ultrastructural examination of the feline and canine vestibular labyrinth, and it does not interfere with DNA analysis via PCR. This technique is feasible for multimodal investigation of the vestibular labyrinth retrieved from individual necropsy cases.