Effect of nocistatin in pain modulation

Using tail-flick latency as the nociceptive index and von Frey hair to meas ure the mechanical allodynia, the aim of the present study is to determine whether nocistatin, injected intracerebroventricularly (i.c.v.), would reve rse the anti-morphine effect of orphanin FQ (OFQ), and, injected i.c.v. or intrathecally (i.t.), would inhibit the mechanical allodynia in a L5 and L6 spinal nerve ligation model of neuropathic pain in rats. The results show that i.c.v. injection of nocistatin produces no significant changes in the TFL, nor does it affect morphine analgesia, In addition, i.c.v. or i.t. noc istatin produces no significant changes in withdrawal threshold of the nerv e-lesioned hind paw. However, nocistatin significantly reverses the antagon istic effect of OFQ on morphine analgesia when it was coinjected i.c.v. wit h OFQ. The results suggest that nocistatin can reverse the anti-morphine ef fect of OFQ in rat brain, but cannot inhibit the mechanical allodynia of ne uropathic pain in rat brain and spinal cord.