Constitution of the greater splanchnic nerve in the rat

The greater splanchnic nerve originating from the sympathetic ganglia between the 10th and 12th ribs on the dorsal thoracic wall passes through the diaphragm between its medial and lateral erura, to form the celiac plexus around the celiac trunk and superior mesenteric artery in the abdominal cavity. The nerve consists of about 10,000 of nerve fibers and of 25,000 of ganglion cells in its whole length of 2.5 cm; nerve fibers can be divided into myelinated fibers, accounting for less than 6% of total numbers, and unmyelinated fibers, which amount to more 90%. Special attention was not paid to the numerous ganglion cells in terms of their shapes, sizes, and cell organelles except for a small number of binucleate cells. However, the nerve contains remarkable synapses that connect between axon showing flat, elliptical, and cored vesicles and dendrite, between another type of axon having elliptical and cored vesicles and dendrite, and even between dendrite and cell body, in which synaptic vesicles are small spherical and elliptical. These facts can suggest that the greater splanchnic nerve contains more complex structure than has been hitherto described.