A profile of the immediate endocrine, metabolic and behavioural responses following a dual exposure to endotoxin in early life.

Dual exposure to endotoxin on postnatal days (PNDs) 3 and 5 is increasingly being used to model the impact of bacterial challenge, in early life, on long-term health outcomes. Currently, however, little is known about how exposure to endotoxin using this model disrupts systems known to program physiological alterations in later life. The aim of the current study was to define, in Fischer 344 rat pups, a framework of the immediate endocrine, metabolic, and behavioural consequences following challenge with 0.05 mg/kg of endotoxin (Salmonella enteritidis) on PNDs 3 and 5. Circulating corticosterone in endotoxin challenged neonates was significantly elevated at all time points assessed on PND 3 (P<0.05), however, by PND 5 this response was attenuated showing a significant elevation only at 4-h post-injection. In these same pups, glucose levels were significantly reduced by 8-h post-injection on PND 3 and remained significantly lower until 8-h post-injection on PND 5 (P<0.05). Finally, the dams of endotoxin challenged pups, exhibited significantly less arched back nursing (P<0.05) but increased levels of off-nest time across the challenge period (P<0.05). These findings demonstrate that postnatal endotoxin exposure impacts on both endocrine and metabolic activity and that alterations in these two systems may in part be mediated by the impact of endotoxin exposure on maternal behaviour.