Cellular interactions at the central and peripheral terminals of primary sensory neurons

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Primary sensory neurons in the dorsal root ganglion play a fundamental role in the transmission of somatosensory information to the spinal cord and may also contribute to the neural regulation of inflammatory and immune responses in the periphery. Three aspects of the physiologic and molecular properties of dorsal root ganglion neurons require further analysis: a) characterization of the molecular events that regulate the differentiation of sensory neuroblasts into different functional classes of neurons; b) determination of the molecular basis for the specificity of central and peripheral connections formed by functional subsets of sensory neurons; c) identification of the chemical mediators released by the central and peripheral terminals of dorsal root ganglion neurons. Physiological studies indicate that excitatory amino acids, peptides, and possibly, nucleotides are released from primary sensory neurons and mediate both fast and slow synaptic responses in the dorsal horn of the spinal cord. Peptides and nucleotides have also been shown to regulate local blood flow and capillary permeability at the peripheral terminals of the sensory neuron. Cell surface carbohydrate differentiation antigens that delineate functional subsets of dorsal root ganglion neurons have recently been identified with monoclonal antibodies. The two major classes of dorsal root ganglion neurons that convey cutaneous sensory information express globo- and lactoseries carbohydrates. These carbohydrate structures have been implicated in intercellular adhesion and cell transformation in embryonic development and may be involved in cell recognition in the developing spinal cord. The identification of carbohydrate differentiation antigens will also be useful in analyzing the early lineage and development of sensory neurons.