Peripheral inflammation increases the capsaicin sensitivity of dorsal root ganglion neurons in a nerve growth factor-dependent manner.
Inflammation results in a local increase in nerve growth factor production which potentially can modify the properties of nerve growth factor-responsive sensory neurons innervating the inflamed tissue. The sensitivity of primary sensory neurons to the neurotoxin capsaicin is regulated in vitro by nerve growth factor and we have now investigated the effect of complete Freund's adjuvant-induced inflammation on the capsaicin sensitivity of adult rat sensory neurons. Dorsal root ganglion neurons innervating inflamed tissue were identified in vivo by retrograde labelling with the dye Fast Blue. Neuronal capsaicin sensitivity was measured in vitro with a quantitative cobalt-uptake densitometric technique, and was shown to increase significantly five days after inflammation. This increase in sensitivity was dependent on nerve growth factor as it could be inhibited by systemic treatment with nerve growth factor neutralizing antibodies. The enhanced capsaicin sensitivity that results from Freund's adjuvant injection may contribute to inflammatory hyperalgesia.
Nicholas
R S
RS
Department of Anatomy and Developmental Biology, University College London, UK.
Winter
J
J
Wren
P
P
Bergmann
R
R
Woolf
C J
CJ
D000578:Amidines; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D002478:Cells, Cultured; D003720:Densitometry / Q000379:methods; D005456:Fluorescent Dyes; D005528:Foot; D005727:Ganglia, Spinal / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology*; D007249:Inflammation / Q000503:physiopathology*; D008297:Male; D009414:Nerve Growth Factors / Q000037:antagonists & inhibitors / Q000502:physiology*; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D000578:Amidines; D005456:Fluorescent Dyes; D009414:Nerve Growth Factors; C031455:diamidino compound 253-50; D002211:Capsaicin