Pulsed radiofrequency enhances morphine analgesia in neuropathic rats.

This study examined the effects of pulsed radiofrequency (PRF) on sciatic nerve ligation-induced mechanical pain hypersensitivity in rats. The nociceptive threshold was evaluated using the paw pressure vocalization test. Seven days after nerve ligation, animals receiving a single PRF session (120 s/2 Hz/45 V/42°C) on L4-5-6 dorsal root ganglia ipsilateral to a chronic constriction injury (CCI) showed a reduced sensory hypersensitivity at H4 6 and 1 day after PRF as compared with animals without PRF. One day after PRF, the effect of morphine (2 mg/kg, subcutaneous) increased the nociceptive threshold in the no PRF/CCI group and more extensively in PRF/CCI animals. These results showed that PRF might represent an interesting strategy not only to reduce neuropathic pain but also to enhance the efficacy of morphine in patients with neuropathic pain, well known to be opioid resistant.