Early weaning impairs a social contagion of pain-related stretching behavior in mice.

Abstract

Pain sensitivity in mice can be modulated through exposure to familiar individuals. This phenomenon is considered a form of emotional contagion, thought to be an evolutionary precursor of empathy in mammals. In particular, mother-infant interactions early in life can considerably alter empathy development. Here, we demonstrated that pairs of mice that were simultaneously administered with a noxious stimulus (acetic acid) exhibited more pain-related behaviors than when one of the pair was treated with a noxious stimulus. However, these differences disappeared when mice were separated from the dam 1 week earlier than the typical weaning age. Even when mice were alone, when treated with acetic acid, early weaning decreased their pain response. These results suggested that the disruption of mother-infant bonding through early weaning impairs pain contagion and modulates sensitivity to pain.