Delta-Opioid Receptors Play a Role in the Control of Selected Parameters Related to Stress and Brain Plasticity Under Non-stress and/or Stress Conditions.

There is some evidence that delta-opioid receptors may be involved in the brain processes related to neuroprotection. The aim of the present studies was to test the hypothesis that endogenous opioid peptides acting via delta-opioid receptors can protect against stress-induced changes in factors related to brain plasticity and stress hormone release. Forty male adult Wistar rats were used. Half of the animals were exposed to sustained partial restraint stress (hypokinesis) lasting 48 h. Rats were treated with vehicle (isotonic saline) or the delta-opioid receptor antagonist naltrindole (3 mg/kg/ml, s.c.) six times a day. The stressfulness of the model was confirmed by increased plasma concentrations of corticosterone and prolactin, the increase in anxiety behavior in the open field test, as well as the reduction of BrdU incorporation into newly formed DNA in the hippocampus. Treatment with naltrindole potentiated the stress-induced rise in aldosterone concentrations. The blockade of delta-opioid receptors resulted in a decrease in hippocampal BDNF gene expression independently of control or stress conditions. Treatment with naltrindole enhanced plasma concentrations of copeptin, a stable precursor of vasopressin. In conclusion, these results suggest that endogenous opioid peptides might play an inhibitory role in aldosterone release under stress conditions and in the control of vasopressin release independently of stress exposure. Endogenous opioids might stimulate hippocampal gene expression of the important neurotrophic factor BDNF via delta-opioid receptors.

Cumulative cortisol concentrations in hair of patients with atopy are lower than in healthy subjects and are not related to their perceived stress experience.

Patients with atopy were found to exhibit blunted cortisol responses to acute stress stimuli. The aim of this study was to test the hypothesis that cumulative cortisol concentrations in the hair of patients with atopy are lower than in healthy subjects when related to their perceived stress experience. The sample consisted of 31 participants. The most proximal 3 cm of hair (as close to the scalp as possible), reflecting the cumulative cortisol secretion during the previous 3 months, was used for the analysis. Only in 20 subjects (9 patients with atopy and 11 healthy controls), there was a sufficient amount of hair for precise analysis using a new methodology. The results showed lower hair cortisol concentrations in patients with atopy compared to those in controls. The perceived stress scores in patients with atopy and healthy controls were not statistically different. The cortisol concentration/perceived stress score ratios were lower in patients with atopy compared to those in controls. No statistically significant correlation between hair cortisol and long-term experienced stress assessed via perceived stress scale was observed. In conclusion, the cumulative cortisol secretion in the hair of atopic patients is lower than would be expected according to their subjective scores of perceived stress. Most importantly, the previously lower stress hormone increase found in acute stress situations and in children now was confirmed in adult patients with chronic stress load.

Neuroendocrine response to a psychosocial stress test is not related to schizotypy but cortisol elevation predicts inflexibility of semantic memory retrieval.

An altered stress response can contribute to the transition from preclinical psychotic symptoms to the clinical manifestation of schizophrenia and other psychotic disorders. The present study was aimed at testing the hypotheses that (i) the autonomic and neuroendocrine responses under psychosocial stress are dysregulated in individuals with high psychosis proneness (schizotypy); (ii) the magnitude of post-stress autonomic activation and cortisol release predicts alterations in semantic memory retrieval. The study was performed in 73 healthy individuals of both sexes with either high or low schizotypal traits preselected out of 609 individuals using the Schizotypal Personality Questionnaire. A psychosocial stress procedure based on public speech was used as a stress model. We found that individuals with high schizotypy engaged in less adaptive emotional stress-coping strategies than low schizotypy individuals. Yet, the neuroendocrine, immune, and sympathetic activation in response to the stress test was not different between the groups. Irrespective of the exposure to the stressor, individuals with high schizotypy were less fluent when retrieving associations from semantic memory. In addition, we demonstrated that acute psychosocial stress reduced the flexibility of semantic memory retrieval. The post-stress mental inflexibility was reliably predicted by the concomitant elevation of cortisol concentrations in saliva. The present study thus brings novel evidence indicating that the acute psychosocial challenge impairs retrieval flexibility in the semantic domain, which may be due to neuroendocrine activation.

Testosterone but not cortisol concentrations in hair correlate between mothers and their prepubertal children under real-life stress conditions.

The aim of the present study is to test the hypothesis that there is an association between the neuroendocrine state, reflected by testosterone and cortisol concentrations in hair, of the mother and her child under difficult real-life stress conditions (COVID-19 pandemic). The research sample consisted of 45 healthy mothers and their prepubertal children (7 - 11 years) of both sexes. The hair samples of mother-child dyads were collected twice to obtain cumulative stress hormone concentrations from April till the end of June and July till the end of September 2020. Thus, 90 mother-child pairs were analyzed. The results showed that both cortisol and testosterone concentrations were significantly higher in the hair of mothers compared to those in their children. The results of cortisol concentrations in hair do not support the hypothesis stated above. In line with our hypothesis are the results of hair testosterone measurements showing a positive correlation between testosterone concentrations in mothers and their children. With respect to the known relationship of testosterone with aggressive behavior, an important finding is that above-mentioned correlation was particularly strong in women with intense subjective feelings of anger in the investigated three months period. Women with strongly prevalent subjective feelings of sadness failed to show a significant correlation between hair cortisol concentrations in mothers and their children, in spite of the known relationship of cortisol to depressive mood. It may be suggested that chronic testosterone secretion reflects the association between the neuroendocrine function of the mother and her child under real-life stress conditions.