TIME-DEPENDENT DIFFERENTIAL CHANGES OF IMMUNE FUNCTION IN RATS EXPOSED TO CHRONIC INTERMITTENT NOISE

Noise is a highly relevant environmental and clinical stressor. Compar ed to most other experimental stressors, noise is a modest activator o f neuroendocrine pathways that mimic the situation in human health whe re neuroendocrine activation by environmental stressors is often absen t or difficult to establish. Little is known about the effects of nois e exposure on the immune system. In the present work, the effects of a low-intensity chronic intermittent unpredictable noise regimen on var ious parameters of immune function was studied. Male wistar rats were exposed to a randomized noise protocol (white noise, 85 dB, 2-20 kHz) for 10 h per day, 15 min per h over a total period of 3 weeks. Control animals were exposed to ambient sound only. Immune function was monit ored after 24 h, 7 days, and 21 days of noise exposure. Noise induced several significant changes in immune function in a time-dependent dif ferential pattern involving both immunosuppression and immunoenhanceme nt. After 24 h, serum IgM levels were increased and peripheral phagocy tic activity was decreased. Splenic lymphocytic proliferation to mitog ens was significantly decreased after 7 days, but slightly elevated af ter 3 weeks. The activity of splenic NK cells was increased significan tly after 24 h and 7 days, but suppressed after 3 weeks. These results show that various parameters of immune function are affected differen tially over time in a period of chronic mild noise stress, possibly du e to sequential activation of different physiological mechanisms. Copy right (C) 1996 Elsevier Science Inc.