Differential effects of inhalation exposure to PM2.5 on hypothalamic monoamines and corticotrophin releasing hormone in lean and obese rats

► There is marked activation of the paraventricular nucleus after acute exposure to PM2.5 as indicated by increases in the levels of neurotransmitters such as norepinephrine and 5-hydroxyindole acetic acid. However, this activation is not apparent after 3 day exposure to PM2.5 in a lean rat model (Brown Norway rat). ► CRH levels follow the neurotransmitter pattern in these lean rats as well. Acute exposure to PM2.5 produces an increase in CRH levels, while subchronic exposures do not. ► In obese rats, subchronic exposure to PM2.5 increases norepinephrine levels in the paraventricular nucleus but does not increase CRH levels. ► Possible reasons for these differences between lean and obese rats are discussed.