Background
While the effects of the bacterial component and Toll-like receptor-4 (TLR4) agonist, lipopolysaccharide (LPS), on affective behaviour is well described, there is a lack of data concerning the effects of peptidoglycans on behaviour. Amongst others, peptidoglycans activate the intracellular receptors nucleotide-binding oligomerization domain 1 (NOD1) and NOD2. Here, the effects of the NOD1 activator FK565 and NOD2 activator muramyl dipeptide (MDP) were investigated with respect to parameters of immune activation and behaviour.