M.S Ramer*, M.D. Kawaja*, J.T. Henderson#, J.C. Roder#, M.A. Bisby*

* Department of Physiology, Queen's University,
   Kingston, Ontario, Canada
# Samuel Lunenfeld Research Institute, Mount Sinai Hospital
   Program and Development and FetalHealth, 600 University Ave., Toronto, Ontario, Canada

Neuroscience Letters, 251(1),pp. 53-56, 1998

Abstract

Adrenergic sprouts within axotomized dorsal root ganglia (DRG) may contribute to neuropathic pain, and may arise under theinfluence of nerve growth factor (NGF). We investigated effects of chronic constriction injury (CCI) on behavior and sprouting in mice in which NGF overexpression is driven by a glial protein (GFAP) promotor. GFAP-NGF mice were naturally hyper-responsive to radiant heat, and had enhanced ipsilateral responses to thermal and mechanical stimulation following CCI compared to wild-type mice. Sympathetic axons were already present in intact DRG of GFAP-NGF mice. Following CCI,sprouting in ipsilateral and to a lesser extent contralateral DRG occurred in both genotypes; however the sprout density 2 weekspost-lesion was much greater in GFAP-NGF mice. These results demonstrate a connection between the endogenous ectopic over-expression of NGF and (1) neuropathic pain behaviour and (2) sympathetic sprouting in the DRG.

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