Fig. 1.

Long-lasting changes induced by adolescent stress exposure in adult rats. (A) Adolescent male rats (n = 10–12/group) were submitted to restraint stress (RS; at postnatal day [PD]31, PD32, and PD40), footshock (FS; daily through PD31–40); or a combination of FS + RS. At adulthood, animals were tested in the elevated plus-maze (EPM) (PD65), novel-object recognition (NOR) test (PD66–67), and locomotor response to amphetamine (PD68–69). Extracellular recordings of ventral tegmental area (VTA) dopamine (DA) neurons started 1 week after the behavioral experiments (PD77–102). (B) All stressors induced impairment in body weight gain and (C) anxiety-like responses in the EPM. (D) FS and FS + RS also disrupted cognitive function in the NOR test as indicated by a decrease in the discrimination index. Only the combination of FS + RS induced a DA hyper-responsivity as indicated by (E) an augmented locomotor response to amphetamine (0.5 mg/kg; injection is indicated by the dashed line) and (F) an increased number of spontaneously active DA cells which was (G) confined to the lateral VTA. In the VTA recordings, data from 5 animals (3 naïve animals, 1 exposed to RS, and 1 exposed to FS) were excluded due to electrode misplacement. Data are presented as mean ± SEM. *P < .05 vs naive rats.