EFFECTS OF FOOTSHOCK STRESS UPON SPLEEN AND PERIPHERAL-BLOOD LYMPHOCYTE MITOGENIC RESPONSES IN RATS WITH LESIONS OF THE PARAVENTRICULAR NUCLEI

To assess the role of the hypothalamic paraventricular nucleus (PVN) i n mediating stressor-induced immune alterations, male Lewis rats were subjected to a 1-h session of intermittent footshock stress or home ca ge conditions 6 days after receiving bilateral or sham PVN lesions. Sp lenic and peripheral blood lymphocyte proliferative responses to the n on-specific mitogens, concanavalin A (ConA) and phytohemagglutinin (PH A), were subsequently measured as were plasma corticosterone levels. I n sham-operated rats, footshock markedly elevated plasma corticosteron e levels and concurrently suppressed the proliferative responses of pe ripheral blood and splenic lymphocytes. In PVN-lesioned rats, however, the shock-induced suppression of lymphocyte proliferation in the peri pheral blood and the elevation of plasma corticosterone were significa ntly attenuated, while lymphocyte proliferation in the spleen was supp ressed below the level of the sham-treated animals. Thus, by utilizing ablation studies, we have determined that the PVN may play a direct r ole in the alteration of lymphocyte function during stress, and an int act PVN buffers the effect of stress on the responsiveness of spleen l ymphocytes to non-specific mitogens.