Neuroendocrine system factors

Feral and LeGall" have suggested that TBT may affect the neuroendocrine system, interfering with the release of a retrogressive factor from the cerebropleiiral ganglia. The effects of TBT on neuroendocrine function merit further study. 

Hypothalamic-Pituitary-Adrenal (HPA) axis An integrated neuroendocrine system linking the hypothalamus (noradrenaline and corticotropin-releasing factor CRF) with the anterior pituitary (corticotropin or ACTH) and the adrenal cortex (cortisol). 

It now seems probable that specific disturbances occur in the immune system in psychiatric illness that are not artefacts of non-specific stress factor, institutionalization or medication. The known effects of the neuroendocrine system on the immune response, and the recent evidence that receptor sites for neurotransmitters and neuroendocrine factors occur on lymphocytes and macrophages, support the hypothesis that immunological abnormalities may assist in precipitating the symptoms of anxiety and depression, commonly symptoms of major affective disorders. 

The mechanism by which the systemic administration of interferon alfa produces neurotoxicity is unclear, and might result from a complex of direct and indirect effects involving the brain vasculature, neuroendocrine system, neurotransmitters and the secondary cytokine cascade with cytokines which exert effects on the nervous system, for example interleukin-1, interleukin-2, or tumor necrosis factor alfa (363). Whether a clinical effect is directly mediated through the action of a given cytokine or results from a secondary pathway through the induction of other cytokines or second messengers is difficult to determine. 

The mechanisms that evoke activation of the neuroendocrine system remain incompletely understood in patients with DHF. A number of factors have been suggested. Myocardial ischemia, uncontrolled hypertension, and excessive dietary sodium or sodium-retaining... 

The physiology and biochemistry of the human neuroendocrine system is complex, highly variable between individuals, and subject to impacts from the maternal environment. The evidence that the activity of the maternal HPA-axis influences the development of the fetal brain is clear and expected. The fetus does not develop in a bubble that isolates it from the mother the dynamics of maternal stress physiology, whether internally driven or driven by the outside world, must be a factor in the development of the fetal brain and nervous system. 

A variety of immune system products (cytokines, peptides) that function to coordinate the immune response may provide important signals for the neuroendocrine system. Those, currently known to have the most relevance for the neuroendocrine system are interleukins (IL) IL-1, IL-2, IL-6, tumour necrosis factors (TNF) and the interferons (IFN) their major role lies in the physiology of inflammation (infection, tumour growth). Lymphokines enhance the release of dopamine and norepinephrine from the adrenal medulla, the dopamine turnover in the brain and serve as endogeneous neurokines regulating striatal dopaminergic function (Zalcman et ah, 1994). Similarly, the dopamine is involved in the modulation of both TNFa and nitric oxide production by peritoneal macrophages, IL-6 release and inhibition of the TNFa synthesized by adrenal cells (Ritchie et al., 1996). 

Development of models to assess chemical-induced allergic or autoimmune reactions is difficult in that both types of reactions are subject to complex processes, and are idiosyncratic in nature. Factors that must be considered include a large number of genetic as well as phenotypic, neuroendocrine, or environmental factors that are only in part related to the immune system. 

GHRF and GHRIF are peptides secreted by hypothalamic neurons termed neuroendocrine transducers (the name is apt, as these interface between the nervous and endocrine systems). The factors that regulate their secretion are poorly understood but probably involve both nerve impulses originating from within the brain and feedback mechanisms, possibly involving pituitary hormones. 

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