Effect of peripheral lipopolysaccharide injection on dopamine content in murine anterior olfactory nucleus

Norepinephrine turnover rate in the murine locus coeruleus (LC) is known to be enhanced by the intraperitoneal (i.p.) injection of lipopolysaccharide (LPS). Approximately 40% of LC neurons are also known to project to the olfactory bulb (OB) and the anterior olfactory nucleus (AON). Therefore, we investigated whether an i.p. injection of 500 microg LPS could modulate the catecholamine biosynthesis in these sites in 8-week-old C3H/HeN male mice. Unexpectedly, the content of norepinephrine was not elevated in both sites during 6-h-observation after LPS injection. The contents of dopamine and its metabolites in the AON were highly increased at 4 h after LPS injection, whereas those in the OB were not elevated during 6-h-observation. Although the AON has been considered not to belong to the dopaminergic neuron system, our report is the first to show an elevated dopamine content in the AON under a stressful condition such as endotoxemia.