Glutamine-, glutamine synthetase-, glutamate dehydrogenase- and pyruvate carboxylase-immunoreactivities in the rat dorsal root ganglion and peripheral nerve.

Supporting glial cells of the peripheral nervous system include satellite cells of dorsal root ganglia and Schwann cells of peripheral nerves. In the central nervous system, glial cells contain enzymes related to the tricarboxylic acid and glutamine cycles: pyruvate carboxylase, glutamate dehydrogenase, and glutamine synthetase. The present study used immunohistochemistry in the rat peripheral nervous system to determine the cellular distribution of these enzymes along with glutamine. In dorsal root ganglia and peripheral nerves, glutamine and glutamine related enzymes were enriched in satellite and Schwann cells. In the dorsal root ganglia, immunoreactive satellite cells surrounded neurons of all sizes. In peripheral nerve, immunoreactive Schwann cells were most easily observed surrounding large diameter, myelinated axons. These Schwann cells contained immunoreactivity in their cell bodies, nodes of Ranvier, and the rim of cytoplasm outside the myelin sheath. Myelin sheaths were non-immunoreactive. The peripheral glial tricarboxylic and glutamine cycles may be used to produce glutamine for neuronal cell uptake and conversion to glutamate for synaptic transmission. Alternatively, these cycles may function in peripheral glia similar to central nervous system astrocytes for supporting the energy demands of neurons.