A SIMPLE METHOD FOR A SPECIFIC RETROGRADE LABELING OF DORSAL-ROOT ANDSYMPATHETIC-GANGLION CELLS INNERVATING THE KNEE-JOINT OF THE CAT

To examine the biochemical characteristics of primary afferents and sy mpathetic efferents innervating the normal and inflamed knee joint of the cat, the corresponding perikarya have to be labelled retrogradely. In the present study we used an injection of the fluorescent dye Fast Blue through the intact skin and the patellar ligament into the centr e of the knee joint cavity and examined the efficiency of this kind of labelling. The segmental distributions of labelled cell profiles;in c ryostat sections of dorsal root ganglia (DRG) and paravertebral gangli a of the sympathetic trunk agreed with data obtained previously after applying the dye at the transected end of the two main articular nerve s. The soma size distribution of labelled DRG cells was identical to p revious results indicating that the perikarya labelled in the present study may be a representative proportion of the knee joint innervation . Axotomy of the medial and posterior articular nerves reduced the num ber of labelled cell profiles of about 85%. Taken together, these data indicate that an injection of Fast Blue into the knee joint cavity of the cat revealed a highly specific and efficient retrograde labelling of the neuronal cell bodies innervating the knee joint.