Schematic of experimental design.

A.Acute treatment. At PN8 or PN12, pups received nine mild tail shocks (1-sec 0.5mA tail shock, each shock separated by a 4-min interval) without the mother (Shock alone), with the mother (Shock+mother), or were placed in the treatment container and not shocked (Control). During treatment, we assessed their behavioral activity and USV’s and Fos expression in the PAG, amygdala, and PVN of the hypothalamus. In a separate cohort of animals, we assess changed changes in gene expression induced in the amygdala by the three treatment conditions at both ages. B, Chronic treatment over 5 days. Pups were shocked with or without the dam or were not shocked each day for 5 days during the pain sensitive period (PN5-9) or during an age range when the mother’s presence suppresses activation of the amygdala during shock (PN10-14). Adult rats were tested for basal pain thresholds using the thermal plantar test and on the next day for inflammation induced hyperalgesia, with brains removed for Fos after this test. In separate cohorts of adult animals, we assessed affective behaviors using a test for social behavior towards a conspecific and threat-induced behaviors with presentations of a predator odor. Key: USVs- ultrasonic vocalizations; PAG- periaqueductal gray; PVN- periventricular nucleus.