Formaldehyde inhalation & open field behaviour in rats

It has been shown in animal studies that repeated exposure to formaldehyde vapour alters behaviour and memory. Since information is not available on the behavioural consequences of acute formaldehyde exposure, this study was conducted to investigate the influence of single inhalative exposure to formaldehyde on the explorative and locomotor behaviour of adult male and female rats.

Rats were exposed to different concentrations of formaldehyde vapour (0.5, 1.0, 2.5%, corresponding to inhalation chamber concentrations of 1.0, 2.5, and 5.0 ppm, respectively) for 2 h and an open field test was carried out 2 h after the end of exposure (first test) and repeated 24 h thereafter (second test). The parameters examined were crossing of floor squares, sniffing, grooming, rearing, climbing, and defaecation.

In exposed male rats, significant reduction of crossed floor squares, grooming, and wall climbing, and increase in floor sniffing and rearing were observed in the first test. During the second test, males in the groups exposed to 2.5 ppm and 5 ppm crossed significantly higher numbers of squares when compared to controls. Air sniffing, wall climbing, and rearing were altered in all exposed males. Control males showed higher incidence of defaecation in comparison to the values of first test. The formaldehyde-exposed female rats crossed significantly decreased numbers of floor squares in the first test. In females in the 2.5 ppm and 5 ppm groups, decreased grooming and enhanced floor sniffing were observed. In the second test, all exposed females crossed higher numbers of floor squares than controls. Frequencies of air and floor sniffing were higher in females exposed to 2.5 ppm and lower in those exposed to 1 ppm. Defaecation was enhanced in females in the 2.5 ppm group in comparison to the first test.

The results show that formaldehyde inhalation in the concentrations and duration of exposure used in the present experiments significantly influences the locomotor and explorative behaviour of rats after a single exposure in a gender-related manner and that various behavioural components in the exposed animals remains altered even after 24 h.