Antagonistic effect of luzindole in mice treated with melatonin during the infection with the venezuelan equine encephalomyelitis virus.

The effect of Luzindole (LZ) in mice treated with melatonin (MEL) during the infection with the Venezuelan equine encephalomyelitis (VEE) virus was examined. Melatonin (500 microg/Kg b.w.) was administered daily 3 days before and 5 days after the infection. Luzindole (5 mg/Kg b.w.) was injected intraperitoneally 3 days before (pre-infection) or 5 days after (post-infection) the infection. Mortality rates in the infected mice treated both with MEL and LZ were higher than in those treated with MEL alone in which the lowest brain and serum viral titers were detected. On the third post-infection day, viral titers of the MEL + VEE + LZ (pre-infection) group were higher than those of the remainder groups. On the fifth day, viral titers in infected mice were similar to those of the MEL + VEE + LZ (pre-infection) group, but higher than those detected in the MEL + VEE + LZ (post-infection). In conclusion, the protective effect of MEL in mice infected with VEE virus was inhibited by LZ suggesting that this protection is mediated by MEL receptors.