Melatonin effects on serum cytokine profiles of rats with different behavioral parameters in acute emotional stress

The effects of melatonin (epiphyseal neurohormone) on the serum cytokine profiles of rats with different behavioral characteristics were studied after acute emotional stress. One-hour immobilization of animals with simultaneous electrocutaneous stimulation of subthreshold intensity served as the stress model. Acute stress exposure of animals with active behavior led to reduction of the peripheral blood concentrations of pro-inflammatory (IL-1α, IL-1β, IL-2, IFN-γ, granulomonocytic CSF) and anti-inflammatory (IL-4, IL-10) cytokines. Passive rats exposed to emotional stress developed a pronounced increase of pro-inflammatory IL-1β concentration. Reduction of pro-inflammatory cytokine levels in active rats exposed to stress was less pronounced after intraperitoneal preinjection of melatonin (2 mg/kg). In passive animals, exogenous melatonin inverted the poststress changes in the serum levels of pro-inflammatory IL-2 cytokine and of anti-inflammatory IL-4 and IL-10 cytokines. The modulatory effect of melatonin on the cytokine profiles of rats with different behavioral parameters seemed to contribute to adaptation of animals to emotional stress exposure.