Research reportBlood oxygen level-dependent signals via fMRI in the mood-regulating circuit using two animal models of depression are reversed by chronic escitalopram treatment

- Both CUMS and MS rat groups demonstrated depression-like behaviours and cognitive impairment, which could be modified by chronic escitalopram treatment.
- Increased BOLD activation was observed in some brain regions of MS and CUMS animals, such as the bilateral hypothalamus, limbic system, hippocampus and frontal lobe, which are parts of mood-regulating circuit.
- The MS- and CUMS-induced increases in BOLD activation were partially attenuated by chronic escitalopram treatment.

BackgroundPeople exposed to stressful experience are at increased risk of the development of depression. A number of functional imaging studies have found disturbances in the mood-regulating circuit of the stress-exposed depressed patients, although few animal imaging studies have been undertaken addressing the brain functional changes of depression.MethodsTwo rat models of depression: maternal separation (MS) and chronic unpredictable mild stress (CUMS), imitating early life stress and adult stress respectively, were administered with escitalopram. The differences in functional brain changes were determined by blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI).ResultsIncreased BOLD activation was observed in some brain regions of MS and CUMS animals, such as the bilateral hypothalamus, limbic system, hippocampus and frontal lobe, which were parts of mood-regulating circuit. Furthermore, the MS- and CUMS-induced increases in BOLD activation were partially attenuated by chronic escitalopram treatment.ConclusionsThese results suggested hyperactivation of mood-regulating circuit at baseline in the depressed animals exposed to stressful experience, and escitalopram can at least partially reverse these effects.