Synaptic Connections in the Geliac Ganglia

Abstract

The distribution of axons effecting synaptic connections in the celiac ganglia and their modes of termination have been studied in silver preparations of human material and material obtained from normal and experimental animals (cats). The synapses observed involve (1) pericellular and peridendritic nests, (2) arborizations of axons in dendritic glomeruli, and (3) axon terminations in dendritic fasciculi. Synapses of these types have been described by de Castro1 in various autonomic ganglia. The synapses effected by the terminal branches of axons with dendrites in dendritic fasciculi probably are the most common in the celiac ganglia. Every ganglion cell in these ganglia probably is synaptically related to more than one axon. Bilateral section of the splanchnic and vagus nerves and extirpation of the upper lumbar segments of the sympathetic trunks in cats resulted in degeneration of the great majority of the axons which effect synaptic connections in the celiac ganglia but not all of them. Degeneration of only the vagus nerves did not appreciably alter the numbers or distribution of synapses in these ganglia. Section of nerves extending from the celiac ganglia to the stomach and intestine resulted in extensive degeneration of the fibers in the distal portions of the nerves and degeneration of some fibers in the proximal portions. The latter observation supports the assumption that fibers which arise in enteric ganglia join the celiac plexus. The synaptic connections which persist in the celiac ganglia following degeneration of the splanchnic and vagus nerves probably are effected by these fibers. They probably constitute connections through which reflex responses in one segment of the gastrointestinal canal may be elicited by impulses arising in another segment.