Relationship Between Behaviors and Catecholamine Content in Prefrontal Cortex and Hippocampus of Chronically Stressed Rats

Abstract

Abstract. Chronic stress induces over-activation and dysfunction of stress-activated systems, resulting in further brain damage and depressive-like behavior. Depression is a potentially life-threatening disorder that affects people and, therefore, it is one of the most important public health problems. This study examined the effects of chronic restraint stress (CRS: 2 hours × 14 days) on the anxiety-like and depression-like behaviors in rats, as well as on the possible changes in the concentrations of dopamine (DA) and noradrenaline (NA) in the prefrontal cortex and hippocampus. We observed a decrease in the number of entries into open arms and time spent in open arms during the elevated plus-maze test (anxiety-like behavior), as well as the increased immobility during the forced swimming test (depression-like behavior). In addition, we found that CRS increases concentration of NA and decreases concentration of DA in the prefrontal cortex and hippocampus. Also, we recorded a significant correlation between the animal behavior and levels of neurotransmitters in the prefrontal cortex and hippocampus in stress conditions provoked by CRS. The results presented here suggest that there is a relationship between the animal behavior and levels of neurotransmitters in the prefrontal cortex and hippocampus in stress conditions provoked by CRS, which may be important in the research of numerous psychiatric diseases caused by chronic stress.

Modulation of Hippocampal Antioxidant Defense System in Chronically Stressed Rats by Lithium

“…It is known that an increase of monoamine neurotransmitter levels is an important therapeutic strategy for several neuropsychiatric disorders [39]. In the present study, we found that lithium treatment increased both protein levels of hippocampal TH and concentration of DA in chronically stressed rats to the levels found in unstressed animals [6, 7], which indicates that lithium enabled de novo synthesis of hippocampal DA in chronically stressed rats. Lithium may have induced the gene expression of hippocampal TH in stress condition through the activator protein-1 (AP-1) transcription factor pathway [40].…”

“…Our results show that it is possible that lithium has an effect on normalizing neuroplasticity in chronically stressed rats. In addition, in our earlier studies, we found that CRS induced a significant decrease of hippocampal DA concentration [6]. Literature data have confirmed that the decreased concentration of DA was observed in many psychiatric and neurodegenerative disorders, for example, depressive illness and Parkinson's disease [19, 38].…”

“…The literature data have shown that there is a direct involvement of oxidative stress in anxiety-like behavior in rodents [12]. Our earlier research confirmed that chronic restraint stress (CRS) influenced anxiety-like behavior in rats [6]. In the pathophysiology of mood disorders, lithium is known as an effective drug in the long-term stabilization of moods.…”

“…The EPM consisted of four elevated (50 cm) contralateral arms (50 cm long and 10 cm wide) with two opposing arms containing 40 cm high opaque walls, which is in accordance with our previous protocol [6]. On the day of EPM testing, rats were transported into the testing room one cage at a time and testing alternated between CRS animals and CRS+Li animals.…”

“…Normal monoaminergic turnover results from balance among synthesis, degradation, release, and reuptake of monoamines. In our previous studies, we found that chronic restraint stress (CRS) induced significant decrease of both hippocampal dopamine (DA) concentration [6] and protein levels of tyrosine hydroxylase (TH), a “rate-limiting” enzyme of dopamine biosynthesis [7], which confirmed that the hippocampus was particularly sensitive to chronic stress [8, 9]. Data about the dynamics of DA transmission and degradation are very important for understanding dopaminergic turnover.…”