Summary. Postganglionic sympathetic fibers originating in the celiac ganglion can be traced by autoradiography to the stomach, spleen, liver and pancreas.Autoradiography is a method widely used for tracing pathways in the CNS but its use in the peripheral nervous system has been more limited 1-5. Recently Kelts 6 has reported using this method to trace efferent fibers from the left celiac ganglion of cats to the contralateral celiac ganglion, satellite ganglia between the 2 celiac ganglia, and the adrenal gland. The present study followed the postganglionic sympathetic fibers originating in the left celiac ganglion of cats as they extended further to the stomach, spleen, liver and pancreas.Cats were anesthetized with Ketaset and a ventral midline incision was made in order to locate the ganglion. From 5 to 15 gl of tritium-labeled leucine (1 mCi/ml) was injected into the ganglion by means of a Hamilton syringe. Post injection periods from 48 to 98 h allowed for diffusion and anterograde axonal transport of the amino acid. The animals were then anesthetized and transcardially perfusedwith 10% buffered neutral formalin. A portion of the abdominal aorta containing the celiac trunk and the superior mesenteric artery with the celiac and superior mesenteric ganglia intact was removed. Branches of the celiac artery along with their accompanying nerves were traced to the organs studied. Sections of the celiac artery with its surrounding tissue were excised. Tissue from the region of the greater curvature of the stomach, from the superior pole of spleen, from the posterior lobe of the liver and from the omental area of the pancreas about 3 cm from the spleen was removed. All tissue was embedded in paraffin and serially sectioned, The sections were mounted on glass slides and dipped in Kodak NTB 2 emulsion. After a 3-week incubation period the sections were developed in D19 and fixed with Kodak Ektaflo. Ganglionic tissue was stained with 1% cresyl violet, the other tissue with hematoxylin and eosin. All slides were studied using light and darkfield optics. 498In all ganglia studied, 3H-leucine had infiltrated the neurons. Outlines of cell bodies could easily be seen due to dense concentrations of the silver grains ( fig. 1). This heavy labeling could readily be traced from the cell bodies into the nerves leaving the ganglia ( fig. 2). These large nerves branched repeatedly forming a plexus of smaller labeled nerves which accompanied small arteries ( fig. 3). This network of small nerves and blood vessels could be followed to the organs being studied. In addition small labeled nerves in close proximity to blood vessels were found within the stomach, spleen and pancreas ( fig.4). No apparent differences were observed between 48 and 98 h postinjection survival periods. This study demonstrates autoradiographically that nerve cell bodies in the celiac ganglion have postganglionic Summary, 12-O-tettadecanoyl phorbo1-13-acetate (TPA, 1-100 ng/ml) induced a reversible contraction in the hydra, Hydra japonica. Another tumor-promo...