Lipopolysaccharide and interleukin-1beta decrease sucrose intake but do not affect expression of place preference in
1Department of Psychology, Concordia College, 56562, Moorhead, MN 56562, USA. larson@cord.edu
Pharmacology, Biochemistry, and Behavior
|July 18, 2006
Summary
Immune system activation, triggered by LPS or IL-1beta, reduces intake of palatable solutions but not preference for associated environments. This highlights distinct effects on primary versus conditioned reinforcers.
Area of Science:
- Neuroscience
- Immunology
- Behavioral Science
Background:
- Immune system activation can diminish interest in rewarding stimuli.
- Previous studies examined effects of cytokines and lipopolysaccharide (LPS) on behaviors reinforced by primary reinforcers like palatable solutions.
- The current study investigates how immune activation impacts behaviors reinforced by both primary and conditioned reinforcers.
Purpose of the Study:
- To determine if immune system activation differentially affects behaviors maintained by primary versus conditioned reinforcers.
- To assess the impact of LPS and interleukin-1beta (IL-1beta) on sucrose intake (primary reinforcer) and conditioned place preference for sucrose (conditioned reinforcer).
- To examine the influence of motivational state on conditioned place preference.
Main Methods:
- Replication of findings showing immune activation decreases palatable solution intake.
- Utilizing a conditioned place preference procedure in rats.
- Administering LPS and IL-1beta to test effects on sucrose intake and sucrose-associated environment preference.
- Manipulating motivational state (water deprivation vs. free access) to assess its effect on conditioned place preference.
Main Results:
- Both LPS and IL-1beta significantly decreased sucrose intake, confirming effects on primary reinforcement.
- Neither LPS nor IL-1beta affected the expression of a sucrose-induced place preference, indicating no impact on conditioned reinforcement.
- A sucrose-induced place preference was observed in water-deprived rats but not in rats with free access to water, demonstrating sensitivity to motivational state.
Conclusions:
- Immune system activation has differential effects on appetitive behaviors, specifically impacting primary reinforcers more than conditioned reinforcers.
- The findings suggest that the neural pathways mediating primary and conditioned reinforcement may be differentially modulated by immune signals.
- Conditioned place preference is a sensitive measure influenced by the subject's current motivational state.
