PAVLOVIAN CONDITIONING OF LPS-INDUCED RESPONSES - EFFECTS ON CORTICOSTERONE, SPLENIC NE, AND IL-2 PRODUCTION

The present study used a taste aversion paradigm to condition lipopoly saccharide (LPS)-induced suppression of splenic lymphocyte interleukin -2 (IL-2) production, with concurrent measurement of corticosterone pr oduction and splenic norepinephrine (NE) content. In training, two gro ups of rats received saccharin and IP LPS in a paired (P) manner and a third group in a specifically unpaired (U) manner. In the test, the u npaired group (group U) and one of the paired (group P) groups were re exposed (R) to the cue and the other not (NR). An additional group con trolled for the effects of cues (conditional stimulus) and fluid depri vation (negative control; NC). A robust taste aversion in the P-R grou p was accompanied by suppression of IL-2 production, reduced splenic N E content, and elevated corticosterone production, relative to combine d controls (i.e., groups U-R, P-NR,and NC). The conditioned modulation of IL-2 secretion, along with the concomitant alteration of adrenocor tical and sympathetic mediators, supports the involvement of bidirecti onal central nervous-immune system pathways in this paradigm.