Hippocampal expression of aryl hydrocarbon receptor nuclear translocator 2 and neuronal PAS domain protein 4 in a rat model of depression

The transcription factors aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) and neuronal PAS domain protein 4 (NPAS4) may influence emotion and cognitive function by regulating brain-derived neurotrophic factor expression in the hippocampus. We estimated hippocampal ARNT2 and NPAS4 expression in chronic unexpected mild stress (CUMS) rat model. The possible association was investigated between expression of these transcription factors and depressive behaviors. Behavioral tests were conducted before, during, and after 28 days of group housing or isolation plus CUMS. The sucrose solution consumption test was used to assess changes in interest and pleasure-seeking, and the open field test (OFT) was conducted to measure spontaneous activity and exploratory behavior. Expression levels of ARNT2 and NPAS4 were estimated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Compared to controls, rats subjected to isolation plus CUMS exhibited significantly reduced weight gain (t = 9.317, P = 0.000), sucrose consumption (t = 3.756, P = 0.003), horizontal ambulation (t = 2.362, P = 0.041), and number of rearings (vertical motion) (t = 2.268, P = 0.040). Relative hippocampal NPAS4 expression was significantly lower in depression model rats compared to controls (t = 2.995, P = 0.010) but there was no significant difference in hippocampal ARNT2 expression between groups (t = 0.091, P = 0.929). The relationship between the CUMS model of depression and NPAS4 expression requires further exploration.