Effects of stress on catecholamine stores in central and peripheral tissues of long-term socially isolated rats

Abstract

Both the peripheral sympatho-adrenomedullary and central catecholaminergic systems are activated by various psycho-social and physical stressors. Catecholamine stores in the hypothalamus, hippocampus, adrenal glands, and heart auricles of long-term socially isolated (21 days) and control 3-month-old male Wistar rats, as well as their response to immobilization of all 4 limbs and head fixed for 2 h and cold stress (4ºC, 2 h), were studied. A simultaneous single isotope radioenzymatic assay based on the conversion of catecholamines to the corresponding O-methylated derivatives by catechol-O-methyltransferase in the presence of S-adenosyl-l-( 3 H-methyl)-methionine was used. The O-methylated derivatives were oxidized to 3 H-vanilline and the radioactivity measured. Social isolation produced depletion of hypothalamic norepinephrine (about 18%) and hippocampal dopamine (about 20%) stores and no changes in peripheral tissues. Immobilization decreased catecholamine stores (approximately 39%) in central and peripheral tissues of control animals. However, in socially isolated rats, these reductions were observed only in the hippocampus and peripheral tissues. Cold did not affect hypothalamic catecholamine stores but reduced hippocampal dopamine (about 20%) as well as norepinephrine stores in peripheral tissues both in control and socially isolated rats, while epinephrine levels were unchanged. Thus, immobilization was more efficient in reducing catecholamine stores in control and chronically isolated rats compared to cold stress. The differences in rearing conditions appear to influence the response of adult animals to additional stress. In addition, the influence of previous exposure to a stressor on catecholaminergic activity in the brainstem depends on both the particular catecholaminergic area studied and the properties of additional acute stress. Therefore, the sensitivity of the catecholaminergic system to habituation appears to be tissuespecific.

The co-occurrence of zinc deficiency and social isolation has the opposite effects on mood compared with either condition alone due to changes in the central norepinephrine system

“…As a result, we detected reduced brain NE concentrations after SI. This agrees with the findings of previous studies in which the brain NE concentrations of isolated animals were found to be significantly lower than those of the control groups [29,30]. Reductions in brain NE concentrations are associated with anxiety and depressive symptoms [31,32].…”

Effects of Marapuama in the chronic mild stress model: Further indication of antidepressant properties

“…The mechanism of action of POEE appears to involve D 1 dopamine and ␤-noradrenergic receptors, since SCH23390 and propranolol reverse POEE effects on both the tail suspension and forced swimming tests (Piato et al, submitted). There is evidence that both noradrenergic (Sherman and Petty, 1980) and dopaminergic neurotransmission (Harvey et al, 2005;Dronjak and Gavrilovic, 2006) may be altered by stress in certain brain areas, including the hippocampus. While additional evidence is required to elucidate the role of the hippocampus in adaptation to stress, an attenuation of the stress-induced aversive state and consequent emotional impact has been suggested (Tsankova et al, 2006).…”

Chronic stress impacts the cardiovascular system: animal models and clinical outcomes

“…In the first method, movements are restricted by placing animals in an appropriately sized animal holder (121). The second technique requires animals to be immobilized by stretching and fixing their limbs to an underlying board using adhesive tape; a metal loop coil restricts head movements (77). Different time periods have been used to model acute or chronic stresses (68,75,187).…”