The uptake of intravenous horseradish peroxidase by the guinea-pig inferior mesenteric ganglion

The uptake of intravenously injected horseradish peroxidase (HRP) by the neuronal perikarya and SIF cells has been studied in the guinea-pig inferior mesenteric ganglion (IMG). The HRP rapidly penetrated the walls of the blood vessels within the ganglion and was taken up by neurons and SIF cells by means of coated pinocytotic vesicles. HRP reaction product was subsequently found within larger vesicles which were most prominent 6--9 hours after injection. Thirty hours after injection all the neurons and SIF cells within the IMG were free of peroxidase reaction product. The implications of these findings were considered in relation to retrograde axonal transport studies in autonomic neurons.