Figure 3. Nocturnal plasma melatonin levels vary during the development of response against lipopolysaccharide challenge.

Plasma melatonin from naïve (black bar), vehicle injected (white bars), lipopolysaccharide injected (LPS, 0.5 mg/kg; grey bars) or LPS plus melatonin injected (3 mg/kg; grey diagonal striped bars) animals was determined by ELISA. The injections were performed 2 or 6 hours before sacrifice (6 hours after lights off –24 h 00). Data are expressed as mean ± SEM, n = 4–8 per group of at least two different experiments; * significantly different (P<0.05) versus naïve group (black bar); # significantly different (P<0.05) versus the 2 hours vehicle group (white bars).