Influence of melatonin on neutrophil-to-lymphocyte ratio in mammalian blood depending on age of the animal

The influence of melatonin on the age dynamics of neutrophils and lymphocytes was investigated in the blood of laboratory rats kept under different light conditions and predatory mammals, including farmer silver foxes and raccoon dogs kept under natural light (NL). The decrease in the lymphocyte level, increase in the neutrophil content, and changes in the ratio of neutrophils to lymphocytes were detected in aged rats (24 months) kept under natural light (NL) and standard light (LD) and adult silver foxes (2–5 years) kept under natural light compared to juvenile animals. The reduced lymphocyte level and increased neutrophil level in rats under constant light (LL) were revealed at younger ages. The effect of melatonin was detected in aged rats and adult silver foxes and not observed in juvenile animals.