The ultrastructure of membranes in sympathetic ganglia

This review presents some recent observations made on membranes in the mammalian sympathetic ganglia after application of freeze-fracturing and histochemistry. After freeze-fracture clear differences have been found between the neuronal and the satellite cell plasmalemma. The satellite cell plasma membrane exhibits specialized intramembrane particles not found in the neuronal membrane. Freeze-fracture cytochemistry reveals a further difference between the neurons and satellite cells i.e., a higher density of beta-hydroxysterols is present in the satellite cell membrane than in the neuronal membrane. Histochemical methods to localize 5'-nucleotidase, Ca2+-ATPase and Na+/K+-ATPase in the membranes have been utilized. The cytochemical reaction products of 5'-nucleotidase and Ca2+-ATPase were found on the external aspect of the plasma membranes. The Na+/K+-ATPase reaction product was located on the cytoplasmic aspect of the membranes, with most activity seen in the satellite cell membrane. With respect to the intercellular junctions, the presynaptic membranes have been analyzed with the freeze-fracture technique under stimulated and unstimulated conditions and ultrastructural differences have been observed which might be correlated to neurotransmission. Furthermore, gap junctions and tight junctional elements occur between the satellite cells surrounding the neuronal perikarya and their processes.