Intrathecal herpes simplex virus type 1 amplicon vector-mediated human proenkephalin reduces chronic constriction injury-induced neuropathic pain in rats.

In the present study, we investigated the antinociceptive effect of herpes simplex virus type 1 (HSV-1) amplicon vector-mediated human proenkephalin (hPPE) on chronic constriction injury (CCI)-induced neuropathic pain in rats. Male Sprague-Dawley rats were intrathecally administered normal saline (NS), pHSVIRES-lacZ (SHZ) or recombinant HSV-1 amplicon vector pHSVIRES-hPPE-lacZ (SHPZ), respectively. Once a week for 5 weeks after the intrathecal (i.t.) administration, the expression levels of hPPE mRNA and leu‑enkephalin (L-EK) were determined. The paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were measured before CCI (baseline) on day 3 and once a week for 5 weeks after i.t. administration. The results showed that the PWMT and PWTL in the SHPZ group were significantly increased compared to the thresholds before i.t. administration. The antinociceptive effect of SHPZ reached its peak 3 weeks after i.t. administration and was maintained for 5 weeks. In the rats administered vehicle or SHZ, there were no significant differences between the PWMT or PWTL and the thresholds before i.t. administration. These results indicate that a single i.t. administration of HSV-1 amplicon vector-mediated hPPE attenuated CCI-induced hypersensitivity in rats.