Impact of anger emotional stress before pregnancy on adult male offspring

Abstract

Previous studies have reported that maternal chronic stress or depression is linked to an increased risk of affective disorders in progeny. However, the impact of maternal chronic stress before pregnancy on the progeny of animal models is unknown. We investigated the behaviors and the neurobiology of 60-day-old male offspring of female rats subjected to 21 days of resident-intruder stress before pregnancy. An anger stressed parental rat model was established using the resident-intruder paradigm and it was evaluated using behavioral tests. Anger stressed maternal rats showed a significant increase in locomotion and aggression but a reduction in sucrose preference. Offspring subjected to pre-gestational anger stress displayed enhanced aggressive behaviors, reduced anxiety, and sucrose preference. Further, offspring subjected to pre-gestational stress showed significant impairments in the recognition index (RI) on the object recognition test and the number of platform crossings in the Morris water maze test. The monoaminergic system was significantly altered in pre-gestationally stressed offspring, and the expression of phosphorylated cyclic adenosine monophosphate response element binding protein (P-CREB), brain-derived neurotrophic factor (BDNF), and serotonin transporter (SERT) levels in pre-gestational stressed offspring were altered in some brain regions. Fluoxetine was used to treat pre-gestational stressed maternal rats and it significantly reduced the changes caused by stress, as evidenced by both behaviors and neural biochemical indexes in the offspring in some but not all cases. These findings suggest that anger stress before pregnancy could induce aggressive behaviors, cognitive deficits, and neurobiological alterations in offspring.

Keywords: aggressive behavior test; anger emotion; monoamine neurotransmitters; resident intruder paradigm; stress before pregnancy.

Figure 1. Maternal behavioral detection for the control group (Control), anger stress (Stress/Model) and Fluoxetine treated (Fluoxetine administration) groups

(A) The total distance of rat moving in 6 min was measured and recorded as the open-field test score (n=8). (B) The percentage of sucrose solution consumed in total liquid consumption was calculated as sucrose preference in the experiment (n=8). (C) The composite aggression score was calculated and used to evaluate the degree of aggression (n = 8). ^*: P<0.05 versus the control; ^***: P<0.001 versus the control; ^#: P<0.05 versus the model; ^##: P<0.01 versus the model; ^###: P<0.001 versus the model.

Figure 2. Offspring behavioral detection for the control (Control offspring), anger stress (Stress offspring) and Fluoxetine treated (FXT offspring) groups

(A) The total distance of the adult offspring rat moving in 6 min was measured and recorded as the open-field test score (n=11 for both Control offspring and Stress offspring; n=8 for FXT offspring). (B) The percentage of open-arms entries was indicated as OE % in the elevated-plus maze test (n=8). (C) The percentage of time for offspring in open-arms was indicated as OT % in the elevated-plus maze test (n=11). (D) In the object recognition task, the recognition index (RI) was calculated to measure novel object recognition and it was used as the main index for retention (n=6 for Control offspring; n=8 for both Stress offspring and FXT offspring). (E) Escape latency in the Morris water maze test was recorded during Day 4 place-learning and it was used as a measure of acquisition and retrieval of the spatial information necessary to reach the platform location (n=10). (F) On the fifth day of the Morris water maze test, the number of platform crossings was recorded to determine the degree of learning acquired by the rats with respect to the position of the platform in the pool (n=8). (G) The composite aggression score was calculated for the offspring to evaluate the degree of aggression (n=8). ^**: P<0.01 versus the control; ^***: P<0.001 versus the control; ^****: P<0.0001 versus the control; ^##: P<0.01 versus the model; ^###: P<0.001 versus the model.

Figure 3

(A–C) 5-HT levels in the hippocampus (A), hypothalamus (B), and prefrontal cortex (C) of the offspring of each group. (D–F) NE levels in the hippocampus (D), hypothalamus (E), and prefrontal cortex (F) of the offspring of each group. (G–I) DA levels in the hippocampus (G), hypothalamus (H), and prefrontal cortex (I) of the offspring of each group. FXT offspring: adult male offspring of rats from the Fluoxetine administration group. ^*: P<0.05 versus the control; ^**: P<0.01 versus the control; ^***: P<0.001 versus the control; ^#: P<0.05 versus the model. n=6 for all.

Figure 4

Relative levels of BDNF/β-actin in the hippocampus (A) and prefrontal cortex (D) of the offspring of each group. Relative levels of pCREB/CREB in the hippocampus (B) and prefrontal cortex (E). Relative levels of SERT/β-actin in the hippocampus (C) and prefrontal cortex (F). FXT offspring: adult male offspring of rats from the Fluoxetine administration group. ^*: P<0.05 versus the control; ^***: P<0.001 versus the control; ^****: P<0.0001 versus the control; ^##: P<0.01 versus the model; ^###: P<0.001 versus the model; ^####: P<0.0001 versus the model. n=3 for all.

Figure 5. Time course of maternal anger stressing and behavioral detection in the control, anger stress, and Fluoxetine treated groups