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Young-Adult Male Rats' Vulnerability to Chronic Mild Stress Is Reflected by Anxious-Like instead of Depressive-Like Behaviors.

José Jaime HP, Venus BC, Graciela JR, Tania HH, Lucía MM - Neurosci J (2016)

Bottom Line: In a previous study, we found that chronic mild stress (CMS) paradigm did not induce anhedonia in young-adult male rats but it reduced their body weight gain.We found that CMS (1) did not affect sucrose preference, immobility behavior in the forced swimming test, or serum corticosterone; (2) decreased body weight gain; and (3) increased the rat's entries into closed arms of the plus maze and the cumulative burying behavior.These data indicate that young male rats' vulnerability to CMS is reflected as poor body weight gain and anxious-like instead of depressive-like behaviors.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Farmacología Conductual, Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, Calzada México-Xochimilco 101, Colonia San Lorenzo Huipulco, Delegación Tlalpan, 14370 Ciudad de México, DF, Mexico.

ABSTRACT
In a previous study, we found that chronic mild stress (CMS) paradigm did not induce anhedonia in young-adult male rats but it reduced their body weight gain. These contrasting results encouraged us to explore other indicators of animal's vulnerability to stress such as anxious-like behaviors, since stress is an etiologic factor also for anxiety. Thus, in this study, we evaluated the vulnerability of these animals to CMS using behavioral tests of depression or anxiety and measuring serum corticosterone. Male Wistar rats were exposed to four weeks of CMS; the animals' body weight and sucrose preference (indicator of anhedonia) were assessed after three weeks, and, after the fourth week, some animals were evaluated in a behavioral battery (elevated plus maze, defensive burying behavior, and forced swimming tests); meanwhile, others were used to measure serum corticosterone. We found that CMS (1) did not affect sucrose preference, immobility behavior in the forced swimming test, or serum corticosterone; (2) decreased body weight gain; and (3) increased the rat's entries into closed arms of the plus maze and the cumulative burying behavior. These data indicate that young male rats' vulnerability to CMS is reflected as poor body weight gain and anxious-like instead of depressive-like behaviors.

No MeSH data available.


Related in: MedlinePlus

Timeline for experimental manipulations.
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Related In: Results  -  Collection


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fig1: Timeline for experimental manipulations.

Mentions: After determination of baseline sucrose consumption, young-adult male rats were randomly assigned to a control or stress group. The males in the control group (n = 13) were maintained during a period of four weeks without stress, but under similar handling and storage conditions to the stressed animals. The stress group (n = 13) was exposed, during a period of four weeks, to several stressors: white noise (~90 dB), overcrowding (2-3 animals per cage), continuous lighting, soiled cage (250 mL water spilled into bedding), stroboscopic light (300 flashes/min), 45° cage tilt along the vertical axis, and water deprivation. The stressor schedule followed in this study was previously used [13, 17, 18] and it is shown in Table 1. To determine anhedonia development, we used a within-subject design since the effect of stress on hedonic state is progressive and the kinetics of the changes in fluid intake are important to determine the establishment of anhedonia in the animals. Thus, during the first three weeks of CMS, sucrose and water intake was determined weekly, as indicated below. At the fourth week (day 27), the 20 h of water and food deprivation indicated in Table 1 was omitted and at this time the CMS was finished. Afterwards, a behavioral tests battery was performed to evaluate stress vulnerability beyond anhedonia; we used a between-subject design in order to avoid ceiling effects or reduction of exploration originated by repeated animals' exposure to the tests. Then, on day 28, the control and stressed groups were exposed to the elevated plus maze test and, immediately after, to the defensive burying behavior test. On days 29 and 30, animals were evaluated in the forced swimming test (pretest and test, resp., at 2:00 p.m.). Several studies indicate that animal's performance in these behavioral tests is sensible to previous stress exposure, including CMS [19–22]; thus, they could be good indicators of stress vulnerability in the nonanhedonic rats. The tests are described below and the time flow of experimental manipulations is indicated in Figure 1.


Young-Adult Male Rats' Vulnerability to Chronic Mild Stress Is Reflected by Anxious-Like instead of Depressive-Like Behaviors.

José Jaime HP, Venus BC, Graciela JR, Tania HH, Lucía MM - Neurosci J (2016)

Timeline for experimental manipulations.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4940564&req=5

fig1: Timeline for experimental manipulations.
Mentions: After determination of baseline sucrose consumption, young-adult male rats were randomly assigned to a control or stress group. The males in the control group (n = 13) were maintained during a period of four weeks without stress, but under similar handling and storage conditions to the stressed animals. The stress group (n = 13) was exposed, during a period of four weeks, to several stressors: white noise (~90 dB), overcrowding (2-3 animals per cage), continuous lighting, soiled cage (250 mL water spilled into bedding), stroboscopic light (300 flashes/min), 45° cage tilt along the vertical axis, and water deprivation. The stressor schedule followed in this study was previously used [13, 17, 18] and it is shown in Table 1. To determine anhedonia development, we used a within-subject design since the effect of stress on hedonic state is progressive and the kinetics of the changes in fluid intake are important to determine the establishment of anhedonia in the animals. Thus, during the first three weeks of CMS, sucrose and water intake was determined weekly, as indicated below. At the fourth week (day 27), the 20 h of water and food deprivation indicated in Table 1 was omitted and at this time the CMS was finished. Afterwards, a behavioral tests battery was performed to evaluate stress vulnerability beyond anhedonia; we used a between-subject design in order to avoid ceiling effects or reduction of exploration originated by repeated animals' exposure to the tests. Then, on day 28, the control and stressed groups were exposed to the elevated plus maze test and, immediately after, to the defensive burying behavior test. On days 29 and 30, animals were evaluated in the forced swimming test (pretest and test, resp., at 2:00 p.m.). Several studies indicate that animal's performance in these behavioral tests is sensible to previous stress exposure, including CMS [19–22]; thus, they could be good indicators of stress vulnerability in the nonanhedonic rats. The tests are described below and the time flow of experimental manipulations is indicated in Figure 1.

Bottom Line: In a previous study, we found that chronic mild stress (CMS) paradigm did not induce anhedonia in young-adult male rats but it reduced their body weight gain.We found that CMS (1) did not affect sucrose preference, immobility behavior in the forced swimming test, or serum corticosterone; (2) decreased body weight gain; and (3) increased the rat's entries into closed arms of the plus maze and the cumulative burying behavior.These data indicate that young male rats' vulnerability to CMS is reflected as poor body weight gain and anxious-like instead of depressive-like behaviors.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Farmacología Conductual, Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, Calzada México-Xochimilco 101, Colonia San Lorenzo Huipulco, Delegación Tlalpan, 14370 Ciudad de México, DF, Mexico.

ABSTRACT
In a previous study, we found that chronic mild stress (CMS) paradigm did not induce anhedonia in young-adult male rats but it reduced their body weight gain. These contrasting results encouraged us to explore other indicators of animal's vulnerability to stress such as anxious-like behaviors, since stress is an etiologic factor also for anxiety. Thus, in this study, we evaluated the vulnerability of these animals to CMS using behavioral tests of depression or anxiety and measuring serum corticosterone. Male Wistar rats were exposed to four weeks of CMS; the animals' body weight and sucrose preference (indicator of anhedonia) were assessed after three weeks, and, after the fourth week, some animals were evaluated in a behavioral battery (elevated plus maze, defensive burying behavior, and forced swimming tests); meanwhile, others were used to measure serum corticosterone. We found that CMS (1) did not affect sucrose preference, immobility behavior in the forced swimming test, or serum corticosterone; (2) decreased body weight gain; and (3) increased the rat's entries into closed arms of the plus maze and the cumulative burying behavior. These data indicate that young male rats' vulnerability to CMS is reflected as poor body weight gain and anxious-like instead of depressive-like behaviors.

No MeSH data available.


Related in: MedlinePlus