J. Van Steenwinckel, M.-J. Brisorgueil, J. Fischer, D. Vergé, J. A. Gingrich et al.
Université Pierre et Marie Curie, CNRS, UMR 7101, Neurobiologie des Signaux Intercellulaires, Paris, France.
Several lines of evidence suggest that descending serotoninergic facilitatory pathways are involved in neuropathic pain. These pathways may involve 5-HT2A receptors known to play a role in spinal and peripheral sensitization. The implication of this receptor in neuropathy was investigated in a model of peripheral neuropathy induced by 2_,3_-dideoxycytidine, a nucleoside analogue with reverse transcriptase inhibitory properties used in HIV/AIDS therapy. Four days after a single 100 mg/kg i.v. administration in the tail vein, mitochondrial alterations in nociceptive and non-nociceptive dorsal root ganglion cells were observed at the lumbar level. These alterations were not associated with TUNEL labelling or with modification of the total number of dorsal root ganglion cells. At the same time point, 5-HT2A receptor immunolabelling was increased throughout the dorsal horn (by 49.5% in layer II and 57.8% in layer III). The number of 5-HT2A receptor immunoreactive neurons in the dorsal root ganglion was also increased by 30.7%. Four days after 2_,3_-dideoxycytidine administration, rats had developed thermal allodynia as well as mechanical hyperalgesia and allodynia, which dose-dependently decreased after epidural injection of MDL 11,939, a 5-HT2A receptor antagonist. Moreover, 5-HT2A receptor knock-out mice did not develop 2_,3_-dideoxycytidine-induced neuropathy whereas their control littermates displayed a neuropathy comparable to that observed in rats. Our data show that 2_,3_-dideoxycytidine-induced neuropathy is associated with alterations of nociceptive and non-nociceptive peripheral cells and that the 5-HT2A receptor is involved in the peripheral sensitization of nociceptors as well as in a wide central sensitization of dorsal horn neurons.
BIOSEB Instruments Used:
Von Frey Filaments (Bio-VF-M)