Nociceptin (1–7) antagonizes nociceptin‐induced hyperalgesia in mice

Publisher Website
Google Scholar
Abstract
Nociceptin and its N‐terminal fragment, nociceptin (1–7), were administered intrathecally (i.t.) into conscious mice. Nociceptin (3.0 fmol) produced a significant reduction in the nociceptive thermal threshold (hyperalgesia) measured as the tail‐flick and paw‐withdrawal responses. Nociceptin (1–7), injected i.t., at 150–1200 fmol had no significant effect. However, when nociceptin (1–7) (150–1200 fmol) was injected simultaneously with nociceptin (3.0 fmol), nociceptin‐induced hyperalgesia was significantly reduced. Analgesia induced by a high dose (1200 pmol) of nociceptin was not antagonized by co‐administration of nociceptin (1–7) (1200 fmol). These results suggest that N‐terminal fragments of nociceptin formed endogenously could modulate the hyperalgesic action of nociceptin in the spinal cord.British Journal of Pharmacology (1999) 128, 941–944; doi:10.1038/sj.bjp.0702898