The neuroendocrine and behavioral effects of chronic paroxetine treatment were investigated in two rat lines selectively bred for high anxiety-related behavior (HAB) or low anxiety-related behavior ...(LAB) emotionality. In addition to a characteristic behavioral phenotype with markedly passive stress-coping strategies, HAB rats show a hypothalamic vasopressinergic hyperdrive that is causally related to hypothalamic-pituitary-adrenocortical dysregulation as demonstrated in the combined dexamethasone (DEX)/corticotropin-releasing hormone (CRH) test. A total of 8 weeks of chronic paroxetine treatment induced a more active coping strategy in the forced swim test in HAB rats only. In contrast, paroxetine-treated LAB rats did not change their swimming behavior. To investigate the neuroendocrine alterations linked to these behavioral changes, a combined DEX/CRH test was performed. In HAB rats, the paroxetine-induced behavioral changes towards more active coping strategies were accompanied by a normalization of the CRH-stimulated increase in corticotropin (ACTH) and corticosterone secretion. Concomitantly, the hypothalamic vasopressinergic hyperdrive was found to be reduced in HAB but not LAB rats, as indicated by a decrease in vasopressin mRNA expression, whereas vasopressin 1a receptor binding was unaffected. These findings provide the first evidence that the vasopressinergic system is likely to be critically involved in the behavioral and neuroendocrine effects of antidepressant drugs. This novel mechanism of action of paroxetine on vasopressin gene regulation renders vasopressinergic neuronal circuits a promising target for the development of more causal antidepressant treatment strategies.
To investigate the neuroendocrine alterations linked to inborn emotionality in two Wistar rat lines selectively bred for either high (HAB) or low (LAB) anxiety-related behavior, we administered the ...combined dexamethasone (DEX)/corticotropin-releasing hormone (CRH) test. DEX (12:00 m. (noon); 30 μg/kg) resulted in a significantly less efficient suppression of the diurnal increase in the circulating corticotropin (ACTH) levels in the male HAB rats than in the male LAB rats. In addition, plasma ACTH and corticosterone responses to subsequent CRH (7:30 p.m.; 50 ng/kg) were significantly higher in male HAB rats. The rise in ACTH after CRH in the DEX-pretreated male HAB rats points toward an enhanced activity and involvement of endogenous vasopressin synthesized in the hypothalamic paraventricular nucleus (PVN) and acting at pituitary corticotrope cells. We tested this hypothesis by in situ hybridization and in vivo microdialysis, and found an increase in both basal synthesis and release of vasopressin within the PVN of the male HAB rats. As expected, pretreatment with a selective vasopressin type 1 receptor antagonist abolished the CRH-stimulated increase in ACTH secretion in the DEX-pretreated male HAB rats. The results indicate that vasopressin-mediated effects are critically involved in the profound disturbance of the hypothalamic-pituitary-adrenocortical system in male HAB rats, thus revealing striking parallels to the neuroendocrine situation in human depression.
The neuroendocrine and behavioral effects of repetitive transcranial magnetic stimulation (rTMS) were investigated in two rat lines selectively bred for high and low anxiety-related behavior. The ...stimulation parameters were adjusted according to the results of accurate computer-assisted and magnetic resonance imaging-based reconstructions of the current density distributions induced by rTMS in the rat and human brain, ensuring comparable stimulation patterns in both cases. Adult male rats were treated in two 3-day series under halothane anesthesia. In the forced swim test, rTMS-treatment induced a more active coping strategy in the high anxiety-related behavior rats only (time spent struggling; 332% vs. controls), allowing these animals to reach the performance of low anxiety-related behavior rats. In contrast, rTMS-treated low anxiety-related behavior rats did not change their swimming behavior. The development of active coping strategies in high anxiety-related behavior rats was accompanied by a significantly attenuated stress-induced elevation of plasma corticotropin and corticosterone concentrations. In summary, the behavioral and neuroendocrine effects of rTMS of frontal brain regions in high anxiety-related behavior rats are comparable to the effects of antidepressant drug treatment. Interestingly, in the psychopathological animal model repetitive transcranial magnetic stimulation induced changes in stress coping abilities in the high-anxiety line only.
Nanomaterial risk governance requires models to estimate the material flow, fate and transport as well as uptake/bioavailability, hazard and risk in the environment. This study assesses the fit of ...such available models to different stages during the innovation of nano-enabled products. Through stakeholder consultations, criteria were identified for each innovation stage from idea conception to market launch and monitoring. In total, 38 models were scored against 41 criteria concerning model features, applicability, resource demands and outcome parameters. A scoring scheme was developed to determine how the models fit the criteria of each innovation stage. For each model, the individual criteria scores were added, yielding an overall fit score to each innovation stage. Three criteria were critical to stakeholders and incorporated as multipliers in the scoring scheme; the required time/costs and level of expertise needed to use the model, and for risk assessment models only, the option to compare PEC and PNEC. Regulatory compliance was also identified as critical, but could not be incorporated, as a nanomaterial risk assessment framework has yet to be developed and adopted by legislators. In conclusion, the scoring approach underlined similar scoring profiles across stages within model categories. As most models are research tools designed for use by experts, their score generally increased for later stages where most resources and expertise are committed. In contrast, stakeholders need relatively simple models to identify potential hazards and risk management measures at early product development stages to ensure safe use of nanomaterials without costs and resource needs hindering innovation.
Nanomaterial risk governance requires models to estimate the material flow, fate and transport as well as uptake/bioavailability, hazard and risk in the environment. This study assesses the fit of ...such available models to different stages during the innovation of nano-enabled products. Through stakeholder consultations, criteria were identified for each innovation stage from idea conception to market launch and monitoring. In total, 38 models were scored against 41 criteria concerning model features, applicability, resource demands and outcome parameters. A scoring scheme was developed to determine how the models fit the criteria of each innovation stage. For each model, the individual criteria scores were added, yielding an overall fit score to each innovation stage. Three criteria were critical to stakeholders and incorporated as multipliers in the scoring scheme; the required time/costs and level of expertise needed to use the model, and for risk assessment models only, the option to compare PEC and PNEC. Regulatory compliance was also identified as critical, but could not be incorporated, as a nanomaterial risk assessment framework has yet to be developed and adopted by legislators. In conclusion, the scoring approach underlined similar scoring profiles across stages within model categories. As most models are research tools designed for use by experts, their score generally increased for later stages where most resources and expertise are committed. In contrast, stakeholders need relatively simple models to identify potential hazards and risk management measures at early product development stages to ensure safe use of nanomaterials without costs and resource needs hindering innovation.
A quantitative approach to matching existing environmental assessment models to the needs of stakeholders at different stages during innovation of nanomaterials and nano-enabled products.
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