The nicotinic cholinergic system is affected in rats with delayed carbon monoxide encephalopathy

Delayed carbon monoxide (CO) encephalopathy may occur following recovery from acute CO poisoning. However, the mechanism of delayed neuronal injury remains unknown. The nicotinic acetylcholine receptors (nAChRs) have been suggested to play a role in cognitive status in neurodegenerative diseases, including Alzheimer's disease. Therefore, in the current study, we investigated the effect of delayed neuronal CO poisoning on gene expression of nAChRs in the hippocampus of Wistar rats. Behavioral effects (measured by the passive-avoidance test) and histological analyses (hematoxylin-eosin-stained hippocampal cell counts and cell death observations) were also investigated, 21 days after CO exposure for 1 h (1000 ppm for 40 min + 3000 ppm for 20 min). Our findings show cognitive impairment and hippocampal cell death, suggesting our rat model is suitable for studying delayed CO encephalopathy. Expression of nAChR (Chrna3, Chrna4, Chnra7, and Chrnb2) mRNA was assessed using quantitative real-time polymerase chain reaction. Hippocampal Chrna3 expression was significantly decreased, and cerebellar Chrna7 expression significantly increased, in the delayed CO encephalopathy rat model. Thus, the nicotinic cholinergic system may be affected in delayed CO encephalopathy.