Journal of Neurocytology

, Volume 28, Issue 9, pp 743-761

Structural basis of sympathetic-sensory coupling in rat and human dorsal root ganglia following peripheral nerve injury

  • Vera ShinderAffiliated withHebrew University of Jerusalem
  • , Ruth Govrin-LippmannAffiliated withHebrew University of Jerusalem
  • , Shulamith CohenAffiliated withHebrew University of Jerusalem
  • , Michael BelenkyAffiliated withHebrew University of Jerusalem
  • , Polina IlinAffiliated withHebrew University of Jerusalem
  • , Kaj FriedAffiliated withDepartment of Neuroscience, Karolinska Institute
  • , Harold A. WilkinsonAffiliated withDivision of Neurosurgery, Newton-Wellesley Hospital
  • , Marshall DevorAffiliated withHebrew University of Jerusalem

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Tyrosine hydroxylase immunocytochemistry was used to reveal the sympathetic postganglionic axons that sprout to form basket-like skeins around the somata of some primary sensory neurons in dorsal root ganglia (DRGs) following sciatic nerve injury. Ultrastructural observations in rats revealed that these sprouts grow on the surface of glial lamellae that form on the neurons. Sciatic nerve injury triggers glial cell proliferation in the DRG, and the formation of multilamellar pericellular onion bulb sheaths, primarily around large diameter DRG neurons. We infer that these glia participate in the sprouting process by releasing neurotrophins and expressing growth supportive cell surface molecules. Many DRG cell somata, and their axons in intact nerves and nerve end neuromas, express α2A adrenoreceptors intracytoplasmically and on their membrane surface. However, sympathetic axons never make direct contacts with the soma membrane. The functional coupling known to occur between sympathetic efferents and DRG neurons must therefore be mediated by the diffusion of neurotransmitter molecules in the extracellular space. Sympathetic basket-skeins were observed in DRGs removed from human neuropathic pain patients, but the possibility of a functional relation between these structures and sensory symptoms remains speculative.