Involvement of Opioid Peptides in the Analgesic Effect of Spinal Cord Stimulation in a Rat Model of Neuropathic Pain

Spinal cord stimulation (SCS)-induced analgesia was characterized, and its underlying mechanisms were examined in a spared nerve injury model of neuropathic pain in rats. The analgesic effect of SCS with moderate mechanical hypersensitivity was increased with increasing stimulation intensity between the 20% and 80% motor thresholds. Various frequencies (2, 15, 50, 100, 10000 Hz, and 2/100 Hz dense-dispersed) of SCS were similarly effective. SCS-induced analgesia was maintained without tolerance within 24 h of continuous stimulation. SCS at 2 Hz significantly increased methionine enkephalin content in the cerebrospinal fluid. The analgesic effect of 2 Hz was abolished by mu or kappa opioid receptor antagonist. The effect of 100 Hz was prevented by a kappa antagonist, and that of 10 kHz was blocked by any of the mu, delta, or kappa receptor antagonists, suggesting that the analgesic effect of SCS at different frequencies is mediated by different endorphins and opioid receptors.

Automated summary

The analgesic effect of spinal cord stimulation (SCS) in a spared nerve injury model was characterized and its underlying mechanisms were examined. Different frequencies of SCS were found to mediate analgesic effects through different endorphins and opioid receptors.