Norepinephrine and dopamine contribute to distinct repetitive behaviors induced by novel odorant stress in male and female mice.

Exposure to unfamiliar odorants induces an array of repetitive defensive and non-defensive behaviors in rodents which likely reflect adaptive stress responses to the uncertain valence of novel stimuli. Mice genetically deficient for dopamine β-hydroxylase (Dbh-/-) lack the enzyme required to convert dopamine (DA) into norepinephrine (NE), resulting in globally undetectable NE and supranormal DA levels. Because catecholamines modulate novelty detection and reactivity, we investigated the effects of novel plant-derived odorants on repetitive behaviors in Dbh-/- mice and Dbh+/- littermate controls, which have catecholamine levels comparable to wild-type mice.