Maternal separation stress leads to enhanced emotional responses to noxious stimuli in adult rats.

The purpose of the current study was to examine pain processing in adult rats following repeated maternal separation in infancy, a common model of early life stress. Sensory pain processing remained unaltered, as measured using threshold testing of nociception. However, affective pain processing was enhanced as revealed by increased responding during the tonic phase of the formalin test and during the place escape/avoidance test. The pattern of enhanced responses suggests that early life stress alters the emotional response to pain. Further research could determine if this pattern holds true for different pain models, or if post-weaning enrichment could reverse the effects of maternal separation on pain processing.