[The features of defensive behavior of early postnatal C57BL/6 mice in response to the predator odor]

The ontogeny of defensive behavior of laboratory rodents underlying many experimental models has been still poorly understood. In this study, we investigated the age-related features of behavior of 8- and 12-day-old laboratory mice in response to presentation of the predator odor using olfactory discrimination method and determination of sleep and wakefulness states. Transcription factor c-Fos was used as a molecular marker to map the activity of the reticular formation. Neither preference nor avoidance of the predator odor was detected, as assessed by the proportion of time spent in the compartment with this odor. However, a reduction of locomotor activity and an increase in the proportion of sleep were found in 8-day-old mice, which corresponded to the c-Fos expression in the oral pontine reticular nucleus. The increase in the proportion of passive wakefulness was found in 12-day-old mice, it could be regarded as an early form of freezing. Thus, we identified age-specific features of the defensive behavior of early postnatal mice as well as the dynamics of its formation.