Carrageenan-induced inflammation of the hind foot provokes a rise of GABA-immunoreactive cells in the rat spinal cord that is prevented by peripheral neurectomy or neonatal capsaicin treatment.

An increase in the number of gamma-aminobutyric acid (GABA)-immunoreactive cells is reported in the superficial dorsal horn of the rat spinal cord upon unilateral inflammation of the hind foot caused by subcutaneous carrageenan injection. The rise of GABAergic cells was restricted to the ipsilateral dorsal horn, reaching a peak value of 23.4% over the contralateral side 4 days after carrageenan injection. Sciatic neurectomy or neonatal capsaicin treatment prevented this effect. These findings suggest that dorsal horn GABA is up-regulated by the increase of noxious inflow conveyed by unmyelinated C fibers from the inflamed tissues.