Seasonal Changes in Behavioral and Psycho-Emotional Responses of Inbred Wistar Rats under Normal and Stress Conditions.

We studied seasonal differences in the fundamental components of behavior and the psycho-emotional status of sexually mature male inbred Wistar rats in winter and spring under normal conditions and after single mild stress exposure (swimming in warm water for 10 min). Behavioral responses were evaluated using standard elevated plus maze (EPM) testing. Psycho-emotional patterns were analyzed by recording typical species-specific postures and reactions in the EPM. No behavioral and hormonal responses to acute stress, as well as biometric changes in the adrenal glands and thymus were revealed during the spring period, when the day length approached its maximum. Possible influence of cross-stressors is discussed. These data should be taken into account when working with laboratory rodents in the spring and winter. The presented data have broad implications for preclinical research and modeling of various pathologies.