Impairments of behavior, information flow between thalamus and cortex, and prefrontal cortical synaptic plasticity in an animal model of depression

Growing evidence suggests the involvement of stress in the pathophysiology of depression. This study was designed to test behavioral and electrophysiological changes in a stressed model of depression. Rats were randomly divided into control and stressed groups. Chronic unpredictable stress combined with isolation rearing was applied in rats of stressed group for three weeks. Weight and sucrose consumption were measured during the model establishing period. Behavior was measured by Morris water maze. Electroencephalography (EEG) of thalamus and prefrontal cortex was recorded after behavioral tests, followed by recording long-term potentiation (LTP) of the same thalamocortical pathway. Results showed that rats’ weight and sucrose intake were significantly lower in stressed group than those in control group. In stressed group, escape latency of reversal training stage in water maze test was significantly prolonged, and platform crossings of reversal probe trials were significantly decreased. EEG test showed that the extent of thalamus driving prefrontal cortex was decreased in stressed group. LTP test showed lower postsynaptic potential amplitude in stressed group as compared to that in control group. In conclusion, chronic stress could cause certain behavioral changes in rats, with possible mechanism of impairing EEG of certain thalamocortical pathway and prefrontal cortical synaptic plasticity.

► Chronic unpredictable stress combined with isolation was used as animal model.
► Chronic stress impaired rats’ reversal learning ability.
► EEG of thalamocortical pathway may be related to stress induced behavioral changes.
► Prefrontal cortical synaptic plasticity might be involved in reversal learning.