Models of Affective Illness: Chronic Mild Stress in the Rat

Abstract

Described in this unit is a chronic mild stress (CMS) procedure used for predicting an antidepressant response. Following exposure to a variety of mild stressors for a period of several weeks, rat behavior is modified in a number of ways. Among these is a substantial reduction in consumption of a 1% sucrose solution. Chronic administration of antidepressant drugs reverses diminished enthusiasm for sucrose in these subjects. While most antidepressants must be administered for at least 3 to 5 weeks to normalize behavior, there are treatments that display a more rapid onset of action. More recently, it has been shown that the CMS-induced deficit in sucrose consumption can also be reversed by second-generation antipsychotics. Based on these findings, the CMS model can be employed in discovery programs aimed at identifying antianhedonic drugs (e.g., antidepressants and antipsychotics) that act more quickly than existing agents.

Antidepressant‐Like Effect of Lipid Extract of Channa striatus in Chronic Unpredictable Mild Stress Model of Depression in Rats

“…The sucrose preference test was conducted on every Sunday morning between 9 and 10 am. The sucrose preference test requires food and water deprivation 24 hr before the test to avoid any nonspecific influence of diet on sucrose consumption [34]. Hence, food and water deprivation was used as the stressor on all Saturdays.…”

“…Since food and water deprivation was used on Saturdays, no other stressors were employed on Saturdays. This was done to avoid any effect of the last stressor on the sucrose consumption [34]. The body weight of each animal was noted on every Sunday before the sucrose preference test.…”

Stress-induced anhedonia is associated with the activation of the inflammatory system in the rat brain: Restorative effect of pharmacological intervention

“…Subsequently, sucrose consumption was monitored, under similar conditions, at weekly intervals throughout the whole experiments. On the basis of their sucrose intake in the final baseline test, animals were divided into two matched groups to be subjected to a chronic mild stress procedure [28] for a period of two (Experiment 1) or seven (Experiment 2) weeks. Each week of the stress regime consisted of two periods of food or water deprivation, two periods of 45 degree cage tilt, two periods of intermittent illumination (lights on and off every 2 h), two periods of soiled cage (250 ml water in sawdust bedding), one period of paired housing, two periods of low intensity stroboscopic illumination (150 flashes/min), and three periods of no stress.…”

Anhedonia but not passive floating is an indicator of depressive‑like behavior in two chronic stress paradigms

“…The list of stressors used is presented in Table I. All of these stressors are usually used for modeling of CUMS (Papp 2012). The stressors were changed twice a day so that each of them was presented for 12-16 h. The animals were exposed to CUMS for 8 weeks.…”