Analgesia induced by neonatal capsaicin treatment in rats.

Twenty-seven rats were treated by 475 mg kg-1 of subcutaneous capsaicin from 2 to 7 days of their life. After treatment, only 11 rats had survived. Their cutaneous heat, pressure, pricking and visceral hyperosmolarity nociceptive thresholds were measured between 50 and 170 days after treatment. The results showed a considerable, or even total, analgesia to cutaneous as well as visceral stimuli. The conclusion is that same pathways carried all the nociceptive messages independently of nature or localization of noxious stimuli.