We studied the effect of acute emotional stress and exogenous IL-1β (5 μg/kg intraperitoneally) on the cytokine profi le of blood serum in Wistar rats with various behavioral characteristics in the open-fi eld test. Blood level of proinfl ammatory cytokine IL-1β decreased in behaviorally passive rats, but increased in active animals after simultaneous immobilization and electrocutaneous stimulation. These changes refl ect the opposite immune responses to a similar stress exposure in rats with different emotional reactivity. Poststress variations in the concentration of circulating IL-1β differed in rats receiving exogenous IL-1β. Blood cytokine concentration decreased in behaviorally active rats, but remained unchanged in passive animals that were exposed to immobilization and electrocutaneous stimulation after pretreatment with IL-1β. Emotional stress and injection of IL-1β had no effect on blood level of an anti-infl ammatory cytokine IL-4 in rats. Our results indicate that rats with various behavioral parameters are characterized by signifi cant differences in the cytokine profi le of blood serum under conditions of emotional stress and treatment with IL-1β. These data illustrate the specifi c functional features of immune mechanisms, which provide an individual resistance of rats to the same stress exposure.A large body of evidence indicates that psychoemotional stress is accompanied by impairment of immune functions in mammals [9]. Immune dysfunction contributes to individual predisposition to stress factors.The pathogenesis of immune dysfunction during emotional stress involves changes in the cytokine profi le. Cytokines are polypeptide transmitters of cellcell interaction playing a regulatory role in normal physiological functions and progression of the defense response to foreign factors and impairment of tissue integrity [1]. Much attention is paid to the superfa mily of IL-1. IL-1β plays a trigger role and induces the cascade of cytokine secretion in the organism. IL-1β is one of the transmitters of the acute phase of the stress response. This cytokine modulates functional activity of the hypothalamic-pituitary-adrenal axis [8]. Our previous studies demonstrated an antistress effect of IL-1β on rats. Intracerebroventricular injection of IL-1β to animals prevents gastric ulceration [3] and involution of the spleen [5] and modulates the oxidative status of the hypothalamus and sensorimotor cortex of the brain under conditions of water-immersion stress [4].
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.
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