Neuropathic pain behavior in rats depends on the afferent input from nerve-end neuroma including histamine-sensitive C-fibers.

Sciatic and saphenous neurectomy in rats produces nerve-end neuromas, known to be a source of afferent input. Concurrently rats self-injure the denervated hindpaw ('autotomy'), a behavior related to neuropathic pain in humans. Here we show that surgical resection of the neuromas in various groups of rats, each at a different postoperative time (days 22, 33, 48) suppress autotomy. This recalls the pain relief in humans following resection of painful neuromas. We also show that daily injections of astemizole, a peripheral anti-histamine which blocks histamine H1-receptors, suppress autotomy. Since mostly C-fibers in rat neuroma are sensitive to histamine, these results corroborate the suggestion that autotomy is driven by afferent neuroma input, mainly in histamine-sensitive C-fibers.