Effect of Lipopolysaccharide Exposure on Structure and Function of the Carotid Body in Newborn Rats

Abstract

Premature infants are vulnerable to infections and have unstable breathing (Di Fiore JM, Martin RJ, Gauda EB, Respir Physiol Neurobiol 189:213-222, 2013). Inflammation adversely modifies carotid body (CB) structure and chemosensitivity in adult animals. We determined the effect of inflammation on CB structure and function in newborn rat pups. Pups were given LPS (0.1 mg/kg; IP) or saline at postnatal day 2 (P2). At P9-10 (1 week after exposure) various studies were done including ventilation, carotid sinus nerve (CSN) activity and histology. Using whole body plethysmography, we found that LPS exposure attenuates the change in interbreath (IBI) interval in response to changes in oxygen tension 1 week after LPS exposure. The response of the CSN to hypoxia was attenuated and delayed in onset in LPS-treated animals as compared to controls. Histological sections of the CB were examined for inflammatory cells at P4 (n = 7) and P9-12 (n = 6). After LPS exposure, only mast cells were seen, often encircling the CB, and clustered within the CSN as it entered the CB. Mast cells per section (mean ± SEM) were higher at P9-12 in LPS (7.4 ± 1.5) vs saline (5.4 ± 1.4) exposed animals (p = 0.04). Surprisingly, more mast cells were seen at 7-10 days vs 48 h after LPS exposure. In a newborn model of inflammation, breathing is altered which is associated with changes in structure and function of the carotid body.