Peripheral modulation of rat knee joint afferent mechanosensitivity by nociceptin/orphanin FQ

The peripheral effects of nociceptin were examined in normal and acutely in flamed rat knee joints by analyzing single unit recordings from articular p rimary afferents in response to normal and extreme rotation of the knee. Bo lus close intraarterial injection of nociceptin (0.01, 1 and 100 mu M) caus ed a sensitization of normal and inflamed knee joint afferents in response to movements in the normal working range of the joint. When the joint was h yper-rotated, nociceptin had no significant effect on afferent discharge ra te in normal knees, however, in inflamed joints the top dose of the neurope ptide caused a decrease in articular mechanosensitivity. These findings sug gest that nociceptin seems to be involved in the control of peripheral noci ceptive mechanisms, although the behaviour of the peptide is dependent upon the inflammatory status of the tissue. (C) 2000 Elsevier Science Ireland L td. All rights reserved.