Effects of cigarette smoke inhalation on spatial memory in mice: the interplay between carbon monoxide and nicotine

Cigarette smoking is a prevalent recreational activity worldwide, spanning all age groups. While the carcinogenic and addictive aspects of smoking are well-recognized, the neurotoxic effects of other toxins like carbon monoxide (CO) in cigarette smoke are often neglected. CO is a known neurotoxin and is produced in significant quantities during smoking. This study aimed to evaluate the impact of CO gas from cigarette smoke on spatial memory in mice. Sixteen adult male mice were divided into two groups: a control group and an experimental group exposed to cigarette smoke (Aspen brand) in a gas chamber (75x50x50 cm) for 15 minutes daily over 14 days. Each group consisted of 8 mice. CO levels were measured using a digital CO meter (PCMM05 Pyle), and spatial memory was assessed using the Barnes maze protocol. Exposure to cigarette smoke resulted in CO levels of up to 347 ppm and an increase in COHb by 16%, exceeding the WHO’s recommended exposure limit of <100 mg/m³ or 87 ppm for 15 minutes and a COHb level of <2%. While spatial memory impairment was observed, the increase in activity likely due to nicotine, a known CNS stimulant, might have mitigated the impact of CO on spatial memory. The memory impairment due to CO exposure might be counteracted by the stimulatory effects of nicotine found in cigarettes.