Influence of early social isolation on general activity and spatial learning in adult WAG/Rij rats

The study identifies the critical period of early ontogeny, during which social factors have the greatest influence on the operant behavior with positive reinforcement in adult WAG/Rij rats. Individual social isolation of rats from dam and siblings was performed daily for 3 h during postnatal day (PND) 2-8, 9-15, and 16-22. General activity and water consumption were examined using the IntelliCage (IC) in adulthood. The operant behavior training was performed in four consecutive sessions: free exploration of the IC environment (adaptation), learning to retrieve water by nosepoking (nosepoke adaptation), spatial learning to retrieve water in the specific corner (place learning), and retraining with a change of a place preference (reversal learning). Social isolation during PND16-22 led to the greatest behavioral changes in all sessions of the experiment. These rats were more active, consumed more water, demonstrated a higher ratio of visits with drinking to the total number, and relearned faster after changing the location of the rewarded corner. Thus, the postnatal period between days 16 and 22 in WAG/Rij rat pups is more sensitive to social isolation for change of adaptive behavior in the IC in adulthood.