Comparison of Marking Changes in Neural Cells Detection Protocol on Superior Laryngeal Nerve in Dogs

Introduction & Neuron tracing is a novel method that is used for detecting communications between cells, tracing nervous pathways, and recognizing the nuclei relating to different pathways. One of the most common tracing methods is putting cutting end of nerve inside the tracer solution. This method is so sensitive that improper insertion of the nerve inside a solution or histological preparation, would lead not to observing the tracers. We evaluated methods for observing tracers. 10 adult dogs were assigned into two groups. In the first group, the superior laryngeal nerve was cut and its proximal end, after washing and des-heating, was put inside the horse radish peroxidase (HRP) solution. In the second group, after washing the proximal cutting end of superior laryngeal nerve, we separated tiny vessels supplying the nerve to prevent hemorrhage. Then, by using the needle (gauge 22), 2-3 distal end of nerve sheath was precisely removed and nerve fibers were separated and kept inside the HRP solution. In both groups, nerve end was kept inside the HRP solution for 2 hours. Three to five days later, after perfusion and fixation their head and neck, their pons, medulla oblongata, three upper spinal segments and vagal ganglions were removed, sectioned and prepared histochemically and stained with thionin. The number of labeled cells in the first group was less (2-4 cells per section) than the second group (4-8 cells). This difference was statistically significant (P < 0.05). This study showed that separating nerve fibers and fixation of nerve end inside the solution increased the absorption of tracer.