Neuroprotective effects of lipopolysaccharide and naltrexone co‑preconditioning in the photothrombotic model of unilateral selective hippocampal ischemia in rat.

Preconditioning with lipopolysaccharide (LPS) or opioid antagonists has a neuroprotective effect in ischemic insults. However, the co‑preconditioning effect of toll‑like receptor ligands and opioid antagonists has not been investigated. In this study we examined the neuroprotective effect of LPS and naltrexone (NTX) preconditioning and co‑preconditioning in unilateral selective hippocampal ischemia in rats to assess for possible synergistic protective effects. LPS and NTX were injected unilaterally into the left cerebral ventricle of male rats. Forty‑eight hours after LPS and twenty‑four hours after NTX injection, ipsilateral selective hippocampal ischemia was induced using a modified version of the photothrombotic method. Protective effects for LPS and NTX were assessed by evaluating infarct volume (using 2,3,5‑triphenyltetrazolium chloride staining), and cognitive function (using radial arm water maze and passive avoidance tests). Animals in the ischemic group had an infarct lesion and considerable cognitive impairment, compared with the sham group. LPS or NTX preconditioning significantly reduced the infarct size and improved cognitive function. Moreover, co‑preconditioning with LPS and NTX increased the protective effect compared with preconditioning with LPS or NTX alone. Our data showed that LPS and NTX preconditioning resulted in a neuroprotective effect in hippocampal ischemia. Furthermore, co‑preconditioning with LPS and NTX resulted in a synergistic protective effect.