Effects of CO2 inhalation exposure on mice vomeronasal epithelium

Abstract

Nasal epitheliums are the first sites of the respiratory tract in contact with the external environment and may therefore be susceptible to damage from exposure to many toxic volatile substances (i.e., volatile organic components, vapors, and gases). In the field of inhalation toxicology, a number of studies have considered the main olfactory epithelium, but few have dealt with the epithelium of the vomeronasal organ (VNO). However, in several species such as in rodents, the VNO (an organ of pheromone detection) plays an important role in social interactions, and alterations of this organ are known to induce adaptative behavioral disturbances. Among volatile toxicants, health effects of inhaled gases have been thoroughly investigated, especially during CO(2) inhalation because of its increasing atmospheric concentration. Therefore, this work was designed to examine the effects of 3% CO(2) inhalation on VNO in two different exposure conditions (5 h/day and 12 h/day) in mice. Behavioral sensitivity tests to urine of congener and histological measurements of VNO were conducted before, during (weeks 1-4), and after (weeks 5-8) CO(2) inhalation exposures. Results showed no significant modifications of behavioral responses to urine, but there were significant changes of both cell number and thickness of the VNO epithelium. Moreover, the findings indicated a selectively dose-dependent effect of CO(2), and further research could use other gases in the same manner for comparison.

Toxicity of Carbon Dioxide: A Review

“…Below its immediately lethal concentration, carbon dioxide has long been considered as a neutral compound for the body. Although few elements are known about its mechanisms of action (Table 2), recent studies raised interest in carbon dioxide in relationship with chronic and/or intermittent long-term exposure conditions that might induce pathologic states, in particular favor DNA alterations, 56 nasal inflammation, 61,62 and pulmonary inflammation. 63,36,64 There are various situations when pCO 2 can rise in inhaled air: first, during professional exposures such as recurrent manipulation of dry ice, food and floral preservation, wearing of masks, spacecraft, aircraft, submarine, altitude, and exposure to gas combustion; 65,33,4 second, during pathological exposures such as sleep apnea, pulmonary diseases (e.g., chronic obstructive pulmonary disease, asthma, emphysema, and chronic bronchitis).…”

“…Below its immediately lethal concentration, carbon dioxide has long been considered as a neutral compound for the body. Although few elements are known about its mechanisms of action (Table ), recent studies raised interest in carbon dioxide in relationship with chronic and/or intermittent long-term exposure conditions that might induce pathologic states, in particular favor DNA alterations, nasal inflammation, , and pulmonary inflammation. ,, …”

Predator odor exposure of rat pups has opposite effects on play by juvenile males and females

“…Exposure of rodents to predator odor elicits an unconditioned fear response (Takahashi et al, 2008). Early life exposure of rat pups to predator odor significantly affects later life behaviors including fear responding (Hacquemand et al, 2010; Ayers et al, 2016). The impact of this early postnatal exposure to predator odor can also differentially affect male and female offspring (Mashoodh et al, 2009).…”

Comparative Fear-Related Behaviors to Predator Odors (TMT and Natural Fox Feces) before and after Intranasal ZnSO4 Treatment in Mice

“…Odorants (a filter paper soaked with 5 μl of 10% TMT, or 5 μl of 10% toluene or 3 g of fox feces) were randomly distributed in the right and the left side of the maze at each test, as well as in the order of testing. At each extremity of the corridor, a hydraulic exhaust fan (2 l/min air) prevented the odorant diffusion in the middle of the maze as used in previous published experiments (Buron et al, 2007, 2009; Hacquemand et al, 2010). …”