Long term alterations in neuroimmune responses of female rats after neonatal exposure to lipopolysaccharide

Male and female rats display significant gender-associated differences in their responses to an immune challenge, and gender-specific alterations in many aspects of physiology are seen after a variety of interventions during the neonatal period. It is well-established that neonatal exposure to an immune challenge can alter centrally mediated inflammatory responses in adult male rats and yet little is known about female responses after a similar challenge. We therefore asked if neonatal exposure to lipopolysaccharide (LPS) would alter febrile and hypothalamic cyclooxygenase (COX)-2 responses to an adult immune challenge in female rats. Female Sprague-Dawley rats were administered a single injection of the bacterial endotoxin LPS at postnatal day 14 and were examined as adults for febrile, COX-2 and activity changes to LPS, as well as responses to interleukin (IL)-1beta. Adult female rat responses were similar to those we have seen previously for the males in that febrile and hypothalamic COX-2 responses to adult LPS were attenuated in neonatally LPS-treated animals. Responses to adult IL-1beta were unaffected. Interestingly, females did not display the elevated basal hypothalamic COX-2 that was previously seen in males. Thus we demonstrate that, like in the males, neonatal exposure to LPS has a powerful effect on adult responses to further LPS challenge in the female rats.