Previous research has demonstrated the conditionability of events within the acute-phase response. This study examined whether two such responses, fever and sleep alterations, were conditionable in the rat during the dark photoperiod. The experimental animals were administered a novel saccharin solution as the conditioned stimulus (CS) in conjunction with lipopolysaccharide as the unconditioned stimulus (UCS). This group displayed significantly higher body temperatures than controls upon saccharin representation, 7 days after the original CS-UCS pairing. The experimental animals additionally displayed a conditioned increase in slow wave sleep (SWS); however, the LPS-induced reduction in rapid eye movement (REM) sleep was unable to be reenlisted. Similar to the acute-response, the conditioned alteration in SWS appeared to be due to an increase in episode frequency, rather than duration. These results suggest that the multiple acute-phase events may be simultaneously conditionable, producing an optimum environment for pathogen elimination.
