Age-Related Changes of the Anxiety Level of Male and Female Rats in Elevated Cross-Maze Test

Age-related peculiarities of formation behavior in the elevated cross-maze was studied in male and female Wistar rats of 6 age groups: the 17-, 21-, 30-, and 36-day-old rat pups as well as adult animals. Recorded were duration of animal stay in the open arms of the maze and the number of hanging-down reactions, parameters of the level of anxiety. In the 17-day-old rat pups the anxiety level was higher than the older animals, the 17-day-old pups being characterized by frequent manifestation of freezing reaction. Duration of stay in the open arms of the maze increased in the 26-day-old rat pups. In the 21-day-old animals the number of hanging reactions rose as compared with the 17-day-old ones, but did not differ from that in the 26-day-old animals. The anxiety level in the 30-day-old rat pups was much lower than in animals of younger age groups. In the rats aged 36 days (the age directly preceding sexual maturation) there was a pronounced enhancement of anxiety, recorded using both parameters. In the 42-day-old animals an increased duration of stay in the open maze arms was again observed, which indicates a decrease of the anxiety level. The obtained data demonstrate complex non-linear development of this form of emotional behavior in ontogenesis and allow suggesting an important role of the hormonal-humoral system in its formation.