BRIEF COMMUNICATION Botulinum Toxin-A Treatment Reduces Human Mechanical Pain Sensitivity and

The mechanisms underlying the analgesic effects of botulinum toxin serotype A (BoNT-A) are not well understood. We have tested the hypothesis that BoNT-A can block nociceptor transduction. Intradermal administration of BoNT-A to healthy volunteers pro-duced a marked and specific decrease in noxious mechanical pain sensitivity, whereas sensitivity to low-threshold mechanical and thermal stimuli was unchanged. BoNT-A did not affect cutaneous innerva-tion. In cultured rodent primary sensory neurons, BoNT-A decreased the proportion of neurons express-ing slowly adapting mechanically gated currents linked to mechanical pain transduction. Inhibition of mecha-notransduction provides a novel locus of action of BoNT-A, further understanding of which may exten