EFFECT OF ONE OR MORE FOOTSHOCKS ON SPLEEN AND BLOOD LYMPHOCYTE-PROLIFERATION IN RATS

The effect of 1 (1.6 mA, 5 s), 3, 8, or 16 inescapable footshocks on t he response of spleen and peripheral blood lymphocytes to nonspecific mitogenic stimulation and plasma corticosterone levels was studied in adult Lewis male rats. One footshock suppressed mitogenic activity in the spleen and this effect was comparable to 3, 8, and 16 footshocks. The maximum suppression to nonspecific mitogenic stimulation in the sp leen was observed at 1 and 10 min after exposure to a single footshock and suppression of the mitogenic responses in the spleen persisted fo r at least 60 min. In contrast, immediately after a single footshock p eripheral blood lymphocyte mitogenic function was not suppressed but i nstead was significantly enhanced. A significant suppression of mitoge nic responsiveness of blood lymphocytes occurred 30 min after exposure to a single footshock and at 60 min the blood mitogenic activity did not differ from the home cage controls. Eight footshocks produced a si gnificant suppression of mitogenic responses in the blood and 16 foots hocks produced the greatest suppression of blood mitogenic function. T hese data suggest that 1 brief footshock caused activation of the HPA axis and sympathetic nervous system and resulted in significant altera tion of the immune system. We suggest that noncomplex models of short- term stress may provide for a better understanding of the mechanisms u nderlying the development of stress reactions in the CNS and the perip hery. (C) 1994 Academic Press, Inc.