Figure 4.

Interactions of (+)‐naltrexone and (+)‐naloxone with the TLR4 antagonist T5342126 in inhibiting LPS‐induced NO in microglial BV‐2 cells. (A) Chemical structure of T5342126; (B, C) BV‐2 cells were treated with LPS (200 ng·mL⁻¹) and different combinations of (+)‐naltrexone/(+)‐naloxone and T5342126 for 24 h. NO in the supernatant was measured by 2,3‐diaminonaphthalene assay and the drug interactions were analysed according to the method described by Chou (2006). CI, combination index, where CI < 1, =1 and >1, indicates synergism, additive effect and antagonism in drug–drug interaction. f _a, fraction affected, that is, fraction of LPS‐induced NO being inhibited by (+)‐naltrexone/(+)‐naloxone and T5342126. Six independent experiments were performed, and the transformed raw data points were shown.