Archival ReportAmygdala-Ventral Pallidum Pathway Decreases Dopamine Activity After Chronic Mild Stress in Rats
Section snippets
Subjects and Materials
Male Sprague-Dawley rats (300–400g; Harlan Laboratories, Hayward, California) were housed for at least 5 days in pairs in a temperature (22°C)- and humidity (47%)-controlled facility upon arrival on a 12-hour light/dark cycle (lights on at 7:00 am) with food and water available ad libitum. Animals were handled in accordance with the guidelines outlined in the United States Public Health Service Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care
Exp 1: CMS-Treated Rats Exhibited Slower Weight Gain, Anxiety-Like Behavior, and Attenuation of VTA DA Neuron Population Activity
Rats were exposed to the CMS procedure (n = 14) or controls (n = 14), with sucrose preference measured in a subgroup of rats (n = 8; CON and CMS, respectively) (Figure 1).
The CMS rats were slower in gaining body weight over the 4 weeks of the CMS procedure (Figure 3A) (ANOVA significant main effect of “week” [F4,104 = 790.86, p < .001], and a significant interaction between “group” and “week” [F4,104 = 3.63, p = .008]). We did not find an alteration in sucrose preference (index of anhedonia) in
Discussion
In this study, we found that the CMS model of depression resulted in a slower body weight gain and development of anxiety- and despair-like behaviors. There was a significant decrease in VTA DA neuron population activity, which was mediated through the BLA-VP pathway. Such decreases in the number of spontaneously firing DA neurons would be expected to greatly lessen the amplitude of the DA response to stimuli (34), which is proposed to decrease the rewarding value of external stimuli.
The CMS
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