2.56 NEONATAL PAIN EXPERIENCED WITH THE CAREGIVER HAS LIFE-LONG CONSEQUENCES FOR PAIN AND EMOTION

Objectives: Human infants born prematurely experience repeated noxious medical procedures, but maternal contact can attenuate the behavioral response to these procedures. However, the mechanisms by which the mother reduces pain or the enduring impact of using the mother as an analgesic stimulus are unknown. By use of an animal model of early life pain with and without the mother, we monitored behavior at different points across the lifespan. Methods: Infant rats were given mild tail shocks (0.5 mA, 1 second every 4 minutes for 32 minutes) either with the mother present or absent for five consecutive days. Two age ranges were chosen to represent the sensitive period for pain programming (PN5-9) and the age at which maternal presence has major neurobehavioral effects, including suppression of amygdala activity (PN10-14). In infancy, neural pain responses were assessed via cFos expression in brain areas associated with pain, as well as behavioral measures related to pain response. In adulthood, pain thresholds, social behavior, and unlearned fear behavior were assessed as a function of infant pain experience. Results: Activity and ultrasonic vocalizations after treatment from PN5-9 and PN10-14 were reduced by the mother's presence during exposure to painful shock. After treatment at PN10-14 pups only, Fos expression in the periaqueductal gray and basolateral and medial amygdala was elevated by the shock alone and reduced by the mother. Adults treated at PN5-9 had reduced carrageenan-induced hyperalgesia and reduced social behavior but no changes in fear behavior if they had undergone pain-mother pairings. In contrast, when treated at PN10-14, the adult had no change in hyperalgesia and showed disruption of social behavior. Shock with or without the mother decreased unlearned fear responding only if treated at PN10-14. The social behavior deficits were normalized by 2 weeks of environmentally enriched rearing after weaning. Conclusions: Our results provide evidence that maternal presence during early life pain reduces pain responses in both infancy and adulthood, but it is also associated with long-term changes in emotionality. The results of these studies aid in our understanding of the impact of nursery procedures that are used to attenuate pain on later outcomes focused on affective behaviors and potentially provide a strategy to reduce those effects.