Peripubertal stress-induced heightened aggression: modulation of the glucocorticoid receptor in the central amygdala and normalization by mifepristone treatment

Abstract

Despite the enormous negative impact of excessive aggression for individuals and societies, there is a paucity of treatments. Here, using a peripubertal stress model of heightened aggression in rats, we investigated the involvement of the glucocorticoid system and tested the effectiveness of antiglucocorticoid treatment to normalize behavior. We assessed peripubertal stress-induced changes in glucocorticoid (GR) and mineralocorticoid (MR) gene expression in different amygdala nuclei and hippocampus, and report a specific increase in GR mRNA expression in the central amygdala (CeA). Administration of mifepristone (10 mg/kg), a GR antagonist, before stressor exposure at peripuberty prevented the habituation of plasma corticosterone responses observed throughout the stress protocol. This treatment also prevented the increase in aggression and GR expression in the CeA observed in peripubertally stressed rats at adulthood. Viral downregulation of CeA GR expression at adulthood led to reduced aggression. Subsequently, we showed that a brief, 3-day, treatment with mifepristone at adulthood was effective to normalize the abnormal aggression phenotype in peripubertally stressed rats. Our results support a key role for GR actions during peripubertal stress for the long-term programming of heightened aggression. Strikingly, they also support the translational interest of testing the effectiveness of mifepristone treatment to diminish reactive aggression in early adversity-related human psychopathologies.

Fig. 1

Effects of peripubertal stress (PPS) on social preference, aggression and GR gene expression. Timeline of the experiment (a). The social preference was lower in stressed rats in comparison to CTRLs (b). PPS animals showed increased percentage of total offensive behavior (c) and frequency of abnormal attacks (e) compared to CTRL rats. The offensive upright percentage did not differ between groups (d). In the central amygdala (CeA), PPS rats showed increased glucocorticoid receptor (GR) mRNA expression without difference in the expression of the mineralocorticoid receptor (MR) (f). No significant change in GR or MR was found in the medial amygdala (MeA) (g), basolateral amygdala (BLA) (h) or CA1 hippocampal region (i). N: social preference: CTRL = 22, PPS = 25; aggression: CTRL = 13, PPS = 16; gene expression: CTRL = 8–9, PPS = 9. *p < 0.05, **p < 0.01, ***p < 0.001, vs CTRL. Results are expressed as mean ± SEM

Fig. 2

Effects of mifepristone treatment prior to peripubertal stress (PPS) on corticosterone, social behaviors and GR gene expression in the central amygdala. Timeline of the experiment (a). Increased corticosterone levels were found in mifepristone-treated stressed rats on P28, P30 and P42 compared to PPS rats injected with the vehicle (b). Stressed rats exhibited a decreased social preference, regardless of the drug treatment, whereas a tendency for increased social preference following mifepristone administration was observed in both groups (c). In the resident-intruder test, PPS animals injected with vehicle showed an increased percentage of attacks, which was normalized following mifepristone treatment (d). A main effect of stress and drug treatment were found in the total offensive behavior duration (e). PPS rats showed higher offensive upright duration than CTRLs (f), whereas a trend toward increased abnormal attacks frequency was observed (g). Gene expression analysis revealed an increased glucocorticoid receptor (GR) mRNA level in the central amygdala (CeA) in PPS vehicle rats, which was normalized with mifepristone treatment (h). N: CTRL vehicle = 8–9; CTRL mifepristone = 8–9; PPS vehicle = 6–9; PPS mifepristone = 8–9. *p < 0.05, **p < 0.01, vs CTRL vehicle, PPS vehicle or main effect of stress. ^#p < 0.05, ^##p < 0.01, ^tp < 0.1 vs vehicle or main effect of drug treatment. Results are expressed as mean ± SEM

Fig. 3

Glucocorticoid receptor (GR) downregulation and social behaviors. Timeline of the experiment (a). Targeted area in the central amygdala and GFP localization with ×4 magnification of the central amygdala are shown in (b). Analysis of GR expression (mRNA) showed a significant decrease in the central amygdala in rats injected with GR downregulating virus (GR-KD) compared to animals with scrambled (SCR) virus (c). DAB immunohistochemistry confirmed the downregulation of GR protein expression in the central amygdala in GR-KD animals (left panel) compared with SCR rats (right panel) with ×40 magnification (d). The social preference was similar among groups (e). GR-KD rats showed decreased total offensive behavior (f), also observed in the offensive upright (g) duration, as compared to SCR animals. The frequency of abnormal attacks (h) was not found to be significantly different between SCR and GR-KD rats. N: SCR rats = 10–12 and GR-KD rats = 11–12, except for resident-intruder data, where GR-KD rats = 6. *p < 0.05, **p < 0.01, vs SCR. Results are expressed as mean ± SEM

Fig. 4

Social behaviors following mifepristone treatment at adulthood. Timeline of the experiment (a). PPS rats showed reduced social preference ratio compared to CTRLs (b). Stressed animals injected with the vehicle exhibited increased total offensive behavior and offensive upright, which were normalized by mifepristone treatment (c and d, respectively). Mifepristone administration reduced the frequency of abnormal attacks in PPS rats (e). N: CTRL vehicle = 14; CTRL mifepristone = 14; PPS vehicle = 12–14 and PPS mifepristone = 13–14. *p < 0.05, **p < 0.01, ***p < 0.001, vs CTRL vehicle, PPS vehicle or main effect of stress. Results are expressed as mean ± SEM