Chronic social isolation in adaptation of HPA axis to heterotypic stress.

Background: Social crowding and isolation are recognized as major stressors and risk factors for development of psychiatric disorders. Chronic isolation stress (IS) and crowding stress (CS) activate neuroendocrine and neurochemical mechanisms, that activate the hypothalamic-pituitary-adrenal (HPA) axis. Changes of the plasma level of interleukin-1β (IL-1β), ACTH and corticosterone (CORT) after chronic psychosocial IS and CS were investigated.

Psychosocial stress inhibits additional stress-induced hyperexpression of NO synthases and IL-1β in brain structures.

Background: The aim of this study was to compare the expression of interleukin-1β (IL-1β), neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in the prefrontal cortex (PFC), hippocampus (HIP) and hypothalamus (HT) during chronic crowding (CS) (psychosocial) and restraint (RS) (physico-psychological) stress. Adaptational changes of these stress mediators to a subsequent acute RS, in two models of chronic stress were investigated.

Methods: Rats were crowded (24 in one cage) or restrained in metal tubes for 10min twice a day for 3, 7, and 14 consecutive days and decapitated.

Cytokines, prostaglandins and nitric oxide in the regulation of stress-response systems.

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis is accepted as one of the fundamental biological mechanisms that underlie major depression. This hyperactivity is caused by diminished feedback inhibition of glucocorticoid (GC)-induced reduction of HPA axis signaling and increased corticotrophin-releasing hormone (CRH) secretion from the hypothalamic paraventricular nucleus (PVN) and extra-hypothalamic neurons. During chronic stress-induced inhibition of systemic feedback, cytosolic glucocorticoid receptor (GR) levels were significantly changed in the prefrontal cortex (PFC) and hippocampus, both structures known to be deeply involved in the pathogenesis of depression.

Brain nitric oxide synthases in the interleukin-1β-induced activation of hypothalamic-pituitary-adrenal axis.

Background: Interleukin-1β (IL-1β), the major cytokine involved in activation of hypothalamic-pituitary-adrenal (HPA) axis modulates both central and peripheral components regulating HPA activity. The role of nitric oxide (NO) generated by neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in brain structures involved in HPA axis regulation has not been elucidated. The aim of the study was to assess the receptor selectivity of IL-1β stimulatory action on HPA axis and to determine the involvement of nNOS and iNOS in this stimulation.

Effect of co-treatment with fluoxetine or mirtazapine and risperidone on the active behaviors and plasma corticosterone concentration in rats subjected to the forced swim test.

Background: Several clinical reports have postulated a beneficial effect of the addition of a low dose of risperidone to the ongoing treatment with antidepressants in treatment-resistant depression.

Methods: The present study aimed to examine the effect of treatment with fluoxetine or mirtazapine, given separately or jointly with risperidone, on active behavior and plasma corticosterone level in male Wistar rats subjected to the forced swim test (FST).

Results: The obtained results showed that fluoxetine (5 mg/kg), mirtazapine (5 and 10 mg/kg) or risperidone (0.

Effect of repeated restraint on homotypic stress-induced nitric oxide synthases expression in brain structures regulating HPA axis.

Background: Restraint stress (RS) markedly increases interleukin 1-β (IL-1β) generation in brain structures involved in hypothalamic-pituitary adrenocortical (HPA) axis regulation. The IL-1β-induced transient stimulation of HPA axis activity was parallel in time and magnitude to respective changes in regulation of HPA activity. In the present experiment the expression of neuron al and inducible nitric oxide synthase (nNOS and iNOS) were investigated in prefrontal cortex, hippocampus and hypothalamus in response to acute restraint stress in control and prior repeatedly restrained rats.

Effect of prior stress on interleukin-1β and HPA axis responses to acute stress.

Interleukin-1β (IL-1β) level is modulated during multiple stress reactions both in brain structures involved in hypothalamic-pituitary-adrenal (HPA) axis regulation and peripheral systems. Multiple distinct stressors induce different IL-1β and HPA axis responses. The purpose of the present study was to determine if the effect of prior repeated restraint stress on IL-1β levels in prefrontal cortex, hippocampus, hypothalamus and plasma may have an impact on alterations induced in HPA axis responses.