The presence of abnormal prion protein accumulation in the pituitary gland and other circumventricular
organs before deposition of [PrP.
These reports support the present results that increased water intake in the second hour of the 2 h feeding period in large-type goats fed on dry forage for 2 h twice daily is the result of increases in plasma osmolality, caused by the ruminal absorption of salts from the consumed feed, that in turn bypassed the blood-brain barrier and activated the osmosenstive neurons in the circumventricular
In addition, the pineal gland is a circumventricular
organ capable of communicating blood signals to the brain through the cerebrospinal fluid .
4) The immune system could be regarded as a "diffuse sensory organ" that signals the presence of pathogens to the brain through different pathways, such as the vagus nerve, endothelial activation/dysfunction which leads to release or passive diffusions of cytokines and neurotoxic mediators, and the circumventricular
organs, especially the neurohypophysis.
Past experiments in which researchers had elecrically stimulated various circumventricular
organs in the brain of mice, including the SFO, had yielded inconsistent results.
Similarly, gastrointestinal hormones act in the central regulation of energy metabolism and show potential sensory roles for the circumventricular
13 One pathway is via macrophagelike cells in the circumventricular
organs and the choroid plexus (lying outside the blood-brain barrier), which detect and respond to circulating pathogen-associated molecular patterns by producing pro-inflammatory cytokines.
cytokines, released by macrophage-like cells in response to pathogens, diffuse through the brain's circumventricular
organs are chemosensitive cells that are highly innervated with fenestrated capillaries.
Particular attention should be paid to lesions in circumventricular
organs and the optic nerve head, since in both regions the blood-brain barrier is less tight than in other regions of the CNS, and AQP-4 is highly expressed at these sites.
However, structures such as the area postrema, median eminence, portions of the hypothalamus, and other circumventricular
organs that lie outside the blood-brain barrier play an integral role in the vomiting reflex.
Other neural afferents and transduction of humoral messages at circumventricular
organs have also been suggested as routes for innate immune system influences on the CNS (Bluthe, Michaud, Kelley, & Dantzer, 1996; Shibata & Blatteis, 1991).